public with sharing class BulkTaskInsertController {
    
    @AuraEnabled
    public static List<Task__c> saveAccounts(List<Task__c> taskList){
        upsert taskList;
        return taskList;
    }
}

import { LightningElement, track,api,wire } from 'lwc';
import { NavigationMixin } from 'lightning/navigation';
import { ShowToastEvent } from 'lightning/platformShowToastEvent';
import saveAccounts from '@salesforce/apex/BulkTaskInsertController.saveAccounts';
import { refreshApex } from '@salesforce/apex';


export default class DynamicRecordCreationRows extends NavigationMixin(LightningElement) {
    
    @api recordId;
    currentProj;
    startDate;
    enddDate;

    @track keyIndex = 0;
    @track error;
    @track message;
    @track taskRecList = [
        {   
            Id:null,           
            Task_Name__c: '',
            Start_Date__c: '',
            End_Date__c: '',
            Description__c:'',
            Project__c:'a005g000001JetFAAS'
        }
    ];

    addRow() {
        this.keyIndex+1;   
        this.taskRecList.push ({ 
            Id:null,           
            Task_Name__c: '',
            Start_Date__c: '',
            End_Date__c: '',
            Description__c:'',
            Project__c:'a005g000001JetFAAS'
        });
        console.log('Enter ',this.taskRecList);
        console.log('Enter ',this.taskRecList);

    }

    changeHandler(event){       
        // alert(event.target.id.split('-'));
         console.log('Access key2:'+event.target.accessKey);
         console.log('id:'+event.target.id);
         console.log('value:'+event.target.value);       
         if(event.target.name==='TaskName')
             this.taskRecList[event.target.accessKey].Task_Name__c = event.target.value;
         else if(event.target.name==='startdate'){
             this.taskRecList[event.target.accessKey].Start_Date__c = event.target.value;
         }
         else if(event.target.name==='enddate'){
             this.taskRecList[event.target.accessKey].End_Date__c = event.target.value;
         }
         else if(event.target.name==='desc'){
            this.taskRecList[event.target.accessKey].Description__c = event.target.value;
        }
     }

     removeRow(event){       
        console.log('Access key2:'+event.target.accessKey);
        console.log(event.target.id.split('-')[0]);
        if(this.taskRecList.length>=2){             
             this.taskRecList.splice(event.target.accessKey,1);
             this.keyIndex-1;
        }
    }  


    saveMultipleTasks() {

        console.log("taskList"+JSON.stringify(this.taskRecList));
        saveAccounts({ taskList : this.taskRecList })
         
                //this.message = result;
                
                .then(() => {
                    this.error = undefined; 
               // this.taskRecList = [];
                console.log(result);
                    refreshApex(this.taskRecList);
                  
                  console.log(this.taskRecList);
                //this.accountRecList = [];
                if(this.message !== undefined) {
                    this.dispatchEvent(
                        new ShowToastEvent({
                            title: 'Success',
                            message: 'Accounts Created!',
                            variant: 'success',
                        }),
                    );
                }
                
                console.log(JSON.stringify(result));
                console.log("result", this.message);
            })
            .catch(error => {
                this.message = undefined;
                this.error = error;
                this.dispatchEvent(
                    new ShowToastEvent({
                        title: 'Error creating records',
                        message: error.body.message,
                        variant: 'error',
                    }),
                );
                console.log("error", JSON.stringify(this.error));
            });
    }

    connectedCallback(){
        this.currentProj=this.recordId;
        alert(this.currentProj+'');
    }

    handleProjectChange(event){
     this.currentProj= event.detail.value;
     alert(this.currentProj);
    }

    //navigate to project 
    navigateToRecordPage() {
        this[NavigationMixin.Navigate]({
            type: 'standard__recordPage',
            attributes: {
                recordId: this.recordId,
                objectApiName: 'Project__c',
                actionName: 'view'
            }
        });
    }

       

}

<template>
    <lightning-card>
        <h3 slot="title">
            <lightning-icon icon-name="standard:task" alternative-text="Event" size="small"></lightning-icon>
            &nbsp;Create New Tasks 
        </h3>
        <template for:each={taskRecList} for:item="item" for:index="index">
            <lightning-record-edit-form key={item.id} object-api-name="Task__c">
                <lightning-messages> </lightning-messages>
                <lightning-layout multiple-rows>
                    <lightning-layout-item size="12" small-device-size="6" medium-device-size="4" large-device-size="2"
                        padding="around-small">
                        <lightning-input name="TaskName" label="Task Name"  access-key={index} id={index} type='text' onchange={changeHandler}  value={item.Task_Name__c} variant="label-stacked" required>
                        </lightning-input>
                    </lightning-layout-item>                    
                    <lightning-layout-item size="12" small-device-size="6" medium-device-size="4" large-device-size="2"
                        padding="around-small">
                        <lightning-input name="startdate" label="Start Date"  access-key={index} id={index} type='date' onchange={changeHandler}  value={item.Start_Date__c} variant="label-stacked" >
                        </lightning-input>
                    </lightning-layout-item>
                    <lightning-layout-item size="12" small-device-size="6" medium-device-size="4" large-device-size="2"
                        padding="around-small">
                        <lightning-input name="enddate" label="End Date"  access-key={index} id={index} type='date' onchange={changeHandler}  value={item.End_Date__c} variant="label-stacked" >
                        </lightning-input>
                    </lightning-layout-item>                    
                    <lightning-layout-item size="12" small-device-size="6" medium-device-size="4" large-device-size="2"
                        padding="around-small">
                        <lightning-textarea name="desc" maxlength="13000" label="Description"  access-key={index} id={index} type='text' onchange={changeHandler}  value={item.Description__c} variant="label-stacked">
                        </lightning-textarea>
                    </lightning-layout-item>
                    
                    <lightning-layout-item size="12" small-device-size="6" medium-device-size="4" large-device-size="2"
                        padding="around-small">
                        <div class="slds-p-top_medium">
                            <lightning-icon icon-name="action:new" access-key={index} id={index}
                                alternative-text="Add Row" size="small" title="Add Row" onclick={addRow}>
                            </lightning-icon>
                            <lightning-icon icon-name="action:delete" access-key={index} id={index}
                                alternative-text="Delete Row" size="small" title="Delete Row" onclick={removeRow}>
                            </lightning-icon>
                        </div>
                    </lightning-layout-item>
                </lightning-layout>

            </lightning-record-edit-form>
        </template>
        </br>
        <lightning-layout>
            <div class="slds-align_absolute-center">
                <lightning-button variant="success" onclick={navigateToRecordPage} name="Cancel" label="Cancel">
                </lightning-button>&nbsp;
                
                <lightning-button variant="success" onclick={saveMultipleTasks} name="quickSave" label="Quick Save">
                </lightning-button>&nbsp;

                <lightning-button variant="success" onclick={saveMultipleTasks} name="save" label="Save">
                </lightning-button>
                
            </div>
        </lightning-layout>
    </lightning-card>
</template>