Hi Marya,
I'm the collections registrar at the Isabella Stewart Gardner Museum, and we have non-accessioned items that we manage--we call them "supplemental holdings" and they are basically a "use" collection made up of historic furniture/furnishings that can be used for office furnishings, exhibitions, conservation treatment training, etc. Most of these items once belonged to our founder and were given back to the museum upon her death. We manage these in our CMS, but with a different numbering system and different collection category designation so it's easy to parse out permanent collection vs. non-permanent. As of right now, language regarding the management of this collection is not included in our CMP (although I want it to be!), but we have a separate procedural document that guides how we manage them, which I'd be happy to share. Given that they are "for use," they are not subject to the same high level standards of care that our permanent collection is, but I maintain registrarial oversight and location control/inventory, and if there is ever any damage to an object, our conservation team will intervene. For acquisitions and disposals from this collection, right now we only require the curator's approval, but the director and collections committee of the board are informed. Once again, since they are not truly accessioned, they do not require a formal deaccession process.
Hope this helps--happy to chat more!
Best,
Kathleen King