macOS menu bar app
View and select the default R version in the macOS menu bar. Start RStudio or a recent RStudio project with the selected R version. Select between your package libraries.
To start the menu bar app the first time, run the Rig app in “Applications” from Finder or Spotlight, or run
open -a Rig
from a Terminal. Then you can check the “Launch at login” box in “Preferences” to start it automatically in the future.

Note: if you have a lot of menu bar apps running on an M1/M2 mac, then some of them might be under the camera area. There is no good solution for this currently, other than running less menu bar apps.