Assign tools to long press — e.g. long press to switch to eraser, release to go back to the previous tool. It’s faster and more reliable than double tap or the current long press toolbar (which isn’t that useful most of the time).

A lot of students at my uni prefer Notability just for this feature — especially since scribble-to-erase isn't always accurate. also the scribble to erase is sometimes not precise enough or just does'nt work 100% of times so long press really is a deal breaker.