I have a stream of builds from some time ago. I now want to purge old builds.
I want to ensure I keep some builds.

The "Keep this build forever" button is not available unless I have enabled
"Discard old builds" in the project configuration. I would like to be able to
mark builds to keep before turning on discard.

A functional work around is to turn on discard with no parameters set (which is
disconcerting because it's not clear what the behavior will be) or with
parameters set so that no build qualifies for discarding. This is also somewhat
bothersome.