How do I hide repositories of closed projects (Google shared drives)?

You can hide folders from your Google Drive navigation panel as follows:

Right click on the specific folder and select “Hide shared drive”.

Google drive menu's options for a drive, including view members, email members, shared drive settings, search, and hide.

To unhide folders:

Click on your Shared Drives folder and then select “Hidden shared drives” on the top right corner.
Right click on the specific folder and select “Unhide shared drive”.