I don’t have any good advice. I made a few quests using the ones in the book as a model and made the major goals  based on important scenes I felt should happen during the quest, and the flavor based on moments or images that felt appropriate (and threw in a few weird or goofy ones for fun). My philosophy and why it didn’t feel so hard was because I was telling myself not to overthink it. Based on the ones in the book quest elements don’t seem like they have to be big powerful things that drive play, but more starting points or inspiration for scenes.