Facing some issue with the build, I deleted the project and .idea directories of my SBT project (containing submodules) followed by Invalidate Caches / Restart... (invalidated the cache too)
Ever since relaunch of IntelliJ, I can't locate the sbt shell

Interestingly, I'm still getting the sbt shell when I open my other projects (in which I didn't delete the project and .idea directories) in IntelliJ

I can confirm that I have the latest release of IntelliJ IDEA for MacOS with the Scala plugin installed

You can select
Window → Restore Default layout
Or press Shift + F12
This will restore your default window layout and the tab will be visible again (You can check this works by hiding the sbt tab by right clicking and selecting 'Remove From Sidebar').
Some windows such as Maven or Ant need to be brought back by
View → ToolWindows → [Window Name]