Just for clarification you mean you want to search for symbols not yet annotated? (and possibly get the view centered on them)
Or do you want some sort of list of what reference designators are available.
Example: some sort of way where kicad tells you the lowest free designator.
Or some way to tell if designators are used in the pcb but don’t have a symbol anymore in the schematic.
I would place the new symbol before deleting the old one. Then edit the reference of the new symbol to be equal to the old one. And finally delete the old symbol. (You can have two symbols with the same reference in kicad. I have not yet decided if i like that.)
FYI I verified the suggestions before I posted them.
Seriously, I wonder why I ever bother to help people. Very rarely do I even get a response, let alone thanks. And then there’s people that argue back with false information. Anyway, you can go on the ignore list.
Either running ERC, or generating a netlist, seems to find the reference-designator errors I’m most likely to make. Of course, no such process is fool-proof because we fools can be VERY ingenious!
Let the two symbols, with identical reference designators, co-exist until you run ERC or generate a netlist. It’s not unusual to keep a superseded symbol on the schematic while you copy some information from it, to a replacement symbol. And sometimes you do a manual re-annotation that makes duplicate reference designators for a short time as you move from one component to another. A couple incarnations ago I used a high-priced EDA tool that did NOT permit duplicate reference designators. It was irritating and aggravating to get a squawk every time you tried to shuffle reference designators.
Yeah, I know how you feel. For over a year now I’ve been trying to throw an occasional joke or humorous comment into my posts and NOBODY has noticed! This group is too serious!