Something I’ve just been bitten by:
Say you have a project in which notes are sorted by Edition date. You realize you actually need to sort the notes manually, because none of the sorting options (Assigned/Creation/Edition dates or title) is appropriate. When notes are sorted by Edition date, dragging a note, to change its order in the note list, is not possible (nothing happens). If you go to the sorting options, there is no “Manual” order option. You have to sort by “Assigned dates”, which has the side effect of enabling manual reordering of notes.
I understand why it works this way: when notes are sorted by assigned dates, notes that have no assigned dates can be reordered manually without clashing with the sort selection. This is not possible with the other sorting options (all notes have Creation dates, Edition dates and titles).
Still, it took me a while to figure out that to sort notes manually I had first to request them to be sorted according to assigned dates (something I did not want to do). It’s been a while since I had to do that and I had forgotten. I’m guessing that this behavior was more intuitive back when Agenda had no sorting option apart from Assigned dates. Newcomers to Agenda might be as confused.
I’m not sure if there is an easy fix.