Navigate to Record Create Page with Auto Populated Field Values in Lightning UI

Navigate to Record Create Page With Auto Populated Field Values

Now, You can create custom button/link to pass the default value to new record page from an Object on Lightning UI.

Please refer the below code

/lightning/o/Account/new?defaultFieldValues=
    Name={!URLENCODE(Account.Name)},
    OwnerId={!Account.OwnerId},
    AccountNumber={!Account.AccountNumber},
    NumberOfEmployees=35000,
    CustomCheckbox__c={!IF(Account.SomeCheckbox__c, true, false)}