Handrail/railing extensions are frustrating. I started with Revit 2016 and I haven't seen any improvements in railings since then. Sometimes you may need a railing style on a particular stair with straight extension on the top and return to post extension at the bottom and then, on another stair, you may need the same railing style but with straight extensions on both the top and the bottom. In order to achieve this, every time you need to do an extension modification you need to duplicate the railing style, select "Top railing" and then duplicate the top railing in order to modify it to a different extension configuration. The process is complicated and not friendly or intuitive.
Railing extensions shouldn't be on a menu inside of another menu.
Suggestion 1: It would be nice if railing extensions were not "by type" but "by instance"
Suggestion 2: It would also be nice if you touched the top or the bottom of a railing an have an extension appear automatically and then, by hitting TAB be able to rotate among different types of extensions until a selection is made.