Is there a capability to add comments in the questions so that users have better idea to understand the question. Also can we add it in the dashboard as well.
You can add question description, which will be shown on the dashboard too as a little gray info-icon next to the question title, which you can hover to display. You edit the description by editing the question:
But if you’re looking for annotations, then there’s a feature request open for that:
https://github.com/metabase/metabase/issues/4838 - upvote by clicking on the first post