This has been brought to my attention by a colleague using 12.9 but it is doing it in 220.127.116.11 too.
Open 2 different database connections but have just one editor window. Open a view (or just write some code) in one tab and switch between database connections. It switches immediately and all is good. Now open a database package script (just one stored as a .pkg file in your file system) and then try the connection switch; this time it takes 15-20 seconds. Switch back and it takes 4-5 seconds. This is all while connected as Apps and the package owner is apps.
When trying the same exercise when connected as something other than Apps, the connection switch takes over a minute - I suspect it is looking through all of the packages in the schema browser. When connected as apps this takes a little while but when not apps, it takes much longer as it needs to refer to synonyms.
We are an ebiz site so the Apps schema has over 45000 packages in it!
I have tried the same thing in 18.104.22.168 and the delay does not happen.