The labels are confusing here. Why is the table occurrence named "sub_account" but you then edit the screen shot to put "Account" above it?
and the occurrence named Sub_acc_class then has "sub account" added above it?
Do you want a name from a field in sub_acc_class to appear on your db_transactions layout?
That will be a problem as the relationship from db_transactions to sub_account to sub_acc_class is many to one to many. When you link a record in db_transactions to sub_account by entering/selecting a value in db_transactions::sub_account, that links you to one sub_account record, but it can link to a group of different records in sub_acc_class. Which record in that group would have the correct name?