I've found that with the 1.8.x series, startup time can be improved by cleaning out the libraries folder.
Moving old sketches out of the way might also help for the startup time.
Cleaning out the temporary directory where the IDE stores temporary stuff can also help in general.
I have 1.8.13 installed; startup takes long but saving, compiling, uploading and exiting are basically instantly.
With the IDE closed, navigate to the library folder, right click the folder and change it from read only, and then delete the folder.
Make a folder to hold the old sketches, select the old sketch folder, and copy it to the old sketches folder, then delete the original folder. MoveTo might work but the folder being set to read only might cause issue or nor.
Remove them from C:\Users\yourUsername\Documents\Arduino\
C:\Users\yourUsername\AppData\Local\Temp; [edit]be careful what you throw away, it's not only arduino stuff in there[/edit].
I have to apologise; I have 1.8.5 installed, not 1.8.13. I'm mostly using 2.0 but if you complain about 1.8.x, you there is a chance that you will also complain about 2.0.
Preparing boards...
2022-11-29T17:21:57.393Z INFO c.a.u.n.HttpConnectionManager:153 [cc.arduino.packages.discoverers.serial.SerialDiscovery] Connect to https://builder.arduino.cc/builder/v1/boards/0x0403/0x6014, method=GET, request id=905F152B31C946C0
Starting...
2022-11-29T17:21:58.038Z INFO c.a.u.n.HttpConnectionManager:157 [cc.arduino.packages.discoverers.serial.SerialDiscovery] Request complete URL="https://builder.arduino.cc/builder/v1/boards/0x0403/0x6014", method=GET, response code=404, request id=905F152B31C946C0, headers={null=[HTTP/1.1 404 Not Found], Cache-Control=[no-cache, no-store, must-revalidate], Server=[nginx], Connection=[keep-alive], Vary=[Origin], Pragma=[no-cache], Expires=[0], Content-Length=[0], Date=[Tue, 29 Nov 2022 17:21:57 GMT]}
2022-11-29T17:21:58.038Z WARN p.a.h.BoardCloudResolver:64 [cc.arduino.packages.discoverers.serial.SerialDiscovery] Fail to get the Vid Pid information from the builder response code=404
ok so far
now the search is virtually useless since one cannot search the entire project
and these tabs cannot be closed as usual
at least I dont have to wait a whole minute before it starts compiling
not that great of a UX
CTRL+F brings the attention of the user on the right of the screen
also
any other editor uses CTRL+SHIFT+F to search the whole project
I mean why reinvent the wheel...C++ and electronics are already complex enough like that...gee