There is often a need to make a new generation of a forms. (example, removing a field requires a new gen form so that the old data is preserved)
There is no way to make both forms visible to users on projects, but only allow the current version to be picked for new projects.
Fully unsharing the old form hides the form (good!), but also hides the data on legacy projects using the form (bad!).
Current approach is to add "ZZZ Retired Form" to the title to push it to the bottom of the list but keep it shared. This title then looks messy on projects.