Would be super useful to be able to edit the values of the Context variables directly from the sidebar, even better if you can add delete but can't be too greedy
You can already delete. Though the icons are far from being accessibility compliant so you may (as I do) struggle to read them.
As for editing - yes, I've occasionally thought that would indeed be useful.
It does not make sense to me that you can't create variables at the place where you can view and delete them.
I think these buttons are too small, they appear "greyed out".
They are the same as the debug panel offers, which evidently don't have sufficient impact, consider the number of people who post a screen capture in preference to the actual data.
Node-red has no right click context sensitive options in the right hand panel. If it did, this would be an appropriate place for such options as "Set context variable", "Delete all [global|flow|node] variables, "Copy value", "Export context" "Set environment variable", etc