What do/did you find to be the most complicated parts of Gramps?

It is worth re-watching the review by an experienced genalogy software user (Ed Thompson, aka @ed4becky ) on the YouTube episode :

It is less painful to watch at 2x speed. (You’ll spend less time telling the screen: “… no. no! NO! That is the hard way to…” )

Or you can read the summary posting. It itemizes the major places where he has obvious difficulties. And each item has hotlinks to skip to that section of the Review.