Flagging active projects?

Having now been using Agenda for several years, I have hundreds of projects, only a few of which are really active at any one moment. Yes, there is the archive function, but most projects fall in between - they are not the immediate priority today, but they are not done either.
I have a similar problem with Mail folders, but macOS Mail has quite a nice mechanism of tagging/untagging them to ‘favourite’, which then adds a Favourites virtual folder at the top of the left side bar - manually sortable. Makes access easier and helps focus on things you have put there.
I wonder if you might consider adding such a mechanism to Agenda.
Best wishes,

Thanks for the suggestion Tim, noted it so we can take it along in our thinking for future updates!