@RikkiMaybe  I have no intention of buying a QBO account to test this, but there is one option you can test.

It was mentioned earlier in the thread that pressing the Tab key moves to the 'Add Line' button, which I assume to be the parallel vertical dots mentioned by one of the staff above.

If that is the case, it is likely that pressing the Spacebar after the Tab key selects that button will trigger the button and add a line.

At least, the Spacebar functions that way in other QuickBooks programs I've used. Not ideal, but at least it will only add a key press to your workflow, rather than a switchover to mouse control.

Best of luck.