Option to join tables or add columns missing for Mondodb

So I started to play around with Metabase and connected my Mongodb datasource. But it seems that option to join data or add columns are missing. Why is that and is there any documentation that could explain it?

Heres the screenshot of what I mean:

Hi @villlem
Some databases has limitations, like MongoDB, as noted in the documentation:
https://www.metabase.com/docs/latest/users-guide/custom-questions.html#joining-data
There’s a feature request for joins:
https://github.com/metabase/metabase/issues/9095 - upvote by clicking :+1: on the first post
This this is the request for Custom Column (aka Custom Field):
https://github.com/metabase/metabase/issues/4946

Thank you very much for the answer. Will do the upvote.