Using the shell the first thing nearly any user does once logged in is run "show dbs" followed by "use xyzdb" followed by "show collections". It would be great to have:

1. Autocomplete on the "show d"<tab> and especially "show c"<tab> the latter I for one nearly always make a typo on
2. Autocomplete on "use "<tab> (looking for db names) because as well as convenience it is a safety feature in that if you make a typo for the db name, then because there is no schema, you can then inadvertently start doing things like inserting records into a new db that didn't previously exist, when you meant to be in an existing db but didn't know because of the typo in the db name.

Show/use autocomplete would be a great paper-cut to eliminate and would be something which is painful in mongo legacy shell today, so a real add value for mongosh