Hi @HarveyL,
I realize that this thread is pretty old, but thought I would share in case others came across this issue as well.
For now, the only way to merge properties is either through the API, or using a custom-coded solution in Operations Hub.
Also, I wanted to share that Insycle can help with this. With Insycle, you can analyze any field in your database, along with the variations of the data contained within that field, to consolidate and retire legacy fields that are creating clutter in HubSpot. Here is our help documentation article for doing this.
Hope that helps!
Best,
Ryan