I use ArcMap 10.4 to manage my ArcGIS Server services, federated with my 10.4 Portal. Occasionally I need to overwrite an existing service (for instance if the schema changes, or if I want to change default symbology). The workflow I follow is, using ArcMap, I go to File-->Share As-->Service-->Overwrite an existing service. The problem with this workflow is that it can overwrite it's corresponding Portal item description, thumbnails, and tags. That is, I have put a lot of work into modifying my Portal item descriptions, thumbnails, tags (the description is HTML formatted not just plain text), the thumbnail is a custom image not a snapshot of the map, and the tags are also custom. I make all these modifications though the Portal UI, but they get overwritten when I publish through ArcMap. Unfortunately I can't add a thumbnail to the map document, nor include HTML formatted description or Summary in the ArcMap Service Editor Item Description section.
Has anyone found a way around this? My only idea so far is to create a backup of all my federated item thumbnails, descriptions, and tags, and use the Python API to modify the items after I've overwritten the service. But this seems labor intensive, and I can't believe no one has solved this problem yet.