Typically it would be one journal entry that would debit and credit those accounts.
Well, not really. Things can get complicated. For customer starting balances, you need to enter unpaid sales invoices separately anyway. If you don’t then once invoices get paid, then your figures on cash-basis won’t be accurate. But even if you don’t use cash-basis reporting, it’s still nice to be able to issue customer their statement with list of unpaid invoices from day 1 of using Manager.
For inventory items, there are like 8 different qty balances tracked for each inventory item. So you need to enter individual orders that haven’t been shipped yet.
Yes - for many accounts, one field Starting Balance is sufficient but even that has proven to be problematic. Many users were going back to these fields continuously and use them to adjust present-time figures to what they wanted them to be without realizing they are affecting their historical balances too.