From Proton Calendar, allow the user to create a recurring annual calendar entry which fall on the 1st, 2nd, 3rd, 4th, or last weekday of the month. For example, US Thanksgiving is always on the 4th Thursday of November. US Memorial Day is always on the last Monday of May. Allow the user to create ad-hoc recurring events similar to those 2 examples within Proton Calendar.

This will also benefit the calendar import feature, as imported calendar entries following the above recurrence rule fail to import currently, since their recurrence pattern is not currently supported by Proton Calendar.