Ability to erase or undo on the spot.
It would be great if one could erase or undo while writing on the page by simply scratching or drawing a line over the character or words similar to the "MyScript Nebo" app. Another option could by a double-tap with two fingers anywhere on the page to undo. While taking notes from long lectures or presentations I find it less practical to look up and move my stylus to the top of the page to hit the undo button or switch to the erase tool. This add-on feature alone will make note taking on Goodnotes a pleasurable experience and bring it to the next level.
Can't praise the scratch to erase feature of Nebo enough!
Of Course, having their text recognition in GoodNotes would be even better...