warning triangles: toggle feature #2280
Description
Consider making the warning triangles toggleable.
At present, we can click on an active warning to deactivate it, however, we cannot re-activate it.
Reactivating a warning would be like marking an email (you have already seen) as unread in order to flag it for future attention. It might be useful for overwhelmed operators.
Note that warnings are propagated up the tree. E.g, if a warning occurs in a/b/c, then the warning triangles will illuminate at the a, a/b and a/b/c levels. Clicking on a would deactivate all warnings in the group (not just a/b/c). This makes sense for deactivating warnings, but we probably don't want to allow groups to be reactivated.