Hi there, sam1968.
Changing the default expense account when adding a new product or service is still not available in QuickBooks Online. This goes the same for the Desktop version since you mentioned that you need to be in a single user mode when making the changes.
For now, you'll need to manually go to the Expense account field (QBO) or COGS Account field to assign the correct account. You can also visit these sites to keep informed of the latest updates and new features that are added in QBO and QuickBooks Desktop:
The Community is always here to help if you need anything else. Thanks!
