It is nice to have recent tags come to the top, but it can make it hard to find tags. It would be nice to also have the option to sort alphabetically.
Actually labels are sorted by the number of items they have. In case you missed it there is a filter option to quickly search your labels:
When I’m trying to quickly sort items by dragging and dropping on labels this is a problem. Filtering requires typing and can’t be done with the mouse, and numerical sorting makes it hard to find the labels.
One really annoying feature of the current system is that tags move after items are added to them, making it harder to find the second time they are used. I suggest a straight alphabetical order, with the 3-5 most recently used items at the top. (As well as in their alphabetical place in the list.)
when starting a new project with some new tags, the pain will appear while finding the correct tag/tags during the literature reviewing process. The reason is the tag position is keep changing due to the current sorting method. Sorting tags alphabetically can keep the constant tag position in the list, more efficient.