Starting Balance

how I can see the entered starting balances ?

Starting balance of which account?

if you want to see starting balances of all accounts, either set the Summary to show the balances on your starting date or under Reports tab generate a Balance Sheet report for the starting date.

@lubos @Tut
I started working on new chart of account from 2019

For this, put the opening balance of all the assets and bank (Other than AP) for the opening balance.

For accounts payable, I entered the back date invoices of all supplier’s by debiting the expenses or assets (whatever is related to).

For example, these back date invoices are now increasing by assets values (Like if I am entering the due invoices with allocating in FA).

Please advise, Should I book only the balance of the suppliers instead of booking the all due invoice for the earlier date?

you should only enter the invoices for which you are yet to make payments to suppliers or yet to receive payments from customers as on the start date.
this is clearly explained in the guide Enter starting balances | Manager

if you want to keep a record of all the other old invoices, you should create appropriate Receipts / Payments transactions also before the start date.

Starting balance is getting affected by Earlier date invoice of AP.

you have not provided enough details to understand what is wrong.
if you believe your starting balance is wrong, then there must be some wrong transaction entered.
it could be posted to a wrong account. or you might have missed to enter a transaction. only you can check and verify your accounts.