To add a new party under the composition scheme but you are unable to save the party master, you need to check the below reasons:
Step 1: First, make sure you add a new party master by pressing F3 in the party option in the voucher window, or you can add it from Administration, then select Masters, then select Account, then select Add. In that window, you should select the dealer type as composition.
Step 2: Also, make sure you have selected the parent group name; without this, you can add a new party.