So I have a few versions of my solution out there, which is nice, but when I want to fix a bug or add an improvement or update to a whole newer version, I have to either add the changes individually to the customer's file, or make a clone of the new version then import all of the tables, update the scripts and value lists, rebuild the accounts....sigh.

I suppose I could write a script to import from each table to the clone, but what about the other items? I could find the differences with FMDiff, but I am hoping there is some kind of updater tool out there that will make this quicker and easier.

Any suggestions greatly appreciated.

I've probably lived through every method.  Yes, you can build a migrator which would import all data into the new version (chaining import scripts). You could use the separation model which might allow you to swap out a UI file . This product has gotten good reviews, but I have not used it. https://www.goya.com.au/refreshfm

Thank you so much, that looks like just what I'm after. I will report back when I have used it.

Please do. I'd like to know how it works out.