If I have to give you a feature that I can no longer work without, it would certainly be "Highlighting variables and fields". This option allows you to highlight a variable (or fields) when you make a full selection of the variable or when you click on a variable.
This is very useful to search for a variable when you have a lot of code and need to know quickly where a certain variable is used.
This replaces the very useful search and highlighting function at the top left of the method editor. Both can be used in complementarity. Highlighting only works for variables and fields so the search function is always very useful.
I'll give you a little GIF that shows how it works.