I am a new user of JIRA. I try to add to an existing board a new project. According to an answer to a similar question the solution is:
Go to the ... at the top right of the Agile board, Configure Board, General, under Filter, right-click "Edit Filter Query".
In the filter, you'll see project in (ABC, ETX). Add the project name to this list.
the problem is that I cannot edit this filter (it is not editable)