Can't find basic boolean operations

[micheus]

Manifoldlab version is maintained by ggaliens user and he has been around, but we don't see any update it has a while.

I would encourage you to try the native booleans present in v2.2.3. although I also would to recommend you to save your project before to use it. At least while you are not confident with it. Dan has working on it for a while and we believe most the errors where removed.
It just don't deal with coplanar faces. You are going to be warned in this situation.