Nor did I say you could or should. I suggested assigning the credit to a special account, which was the entire point here. For example, set up a control account, Gift vouchers. Create a special account for Customer ABC Gift Voucher 12345. Enter a sales invoice:
The only differences between the Guide and my example are (1) the Guide’s control account was Store credit, while mine was Gift vouchers and (2) the Guide’s special account was named only after the customer, while mine included both customer and gift voucher number.
You most certainly can, unless the account is in-built. See the above illustration. The ones you cannot select are those like Accounts receivable or Accounts payable, because they are wrapped up with hard-coded postings connected to customers and suppliers. When you create your own custom control accounts, you are not limited in that way, because there is no underlying hard-coding that might be interfered with.
No, it definitely does not. You added the words “(customers tab).” The actual Guide language is shown in the following screen shot:
The term customers was used only because the example that follows was about a store credit for a customer. So the special account was named after a customer. But nowhere is the Customers tab referenced. And the custom control account was not made up of Customers, but of special accounts. In the preceding paragraph of the Guide, there was mention of using special accounts for loans. Those special accounts might have been named after loan numbers or mortgaged properties or construction equipment purchased.
The fact is, use of special accounts for tracking gift vouchers was one of the purposes for them explicitly mentioned by @lubos when the feature was first introduced in mid-2016 (see the end of the following release note):