That is very poor UI design.
So, just to make sure, do all of the "Set Font" buttons have EXACTLY the same name?
If so, then native KM Actions may not be able to help us in this case.
You could probably click on a specific button using AppleScript UI scripting, by selecting the proper button by element position, or by some internal ID.
The best tool to get the properties of a button is UI Browser, but it is expensive at ~$50. There may be a trial available.
But this tool by Chris @ccstone might be able to give us the data we need:
Front Window Analysis Tool Using AppleScript System Events (get window elements)
If you need help in identifying the button you want in this results list and/or using that in an AppleScript, then please save the BBEdit file (as a .py), zip it, and upload to forum, along with a screenshot of your app windows identifying the button you want to press.