Thanks for this! I was kind of hoping things would have changed/improved since the previous thread.
I ended up adapting your example in that old thread, where you searched and replaced the admin page output. I wanted a button to reside in the middle of a field group, so I added a “Message” field in the group, where the message text is something like FLUSH_API_CACHE, which I then replace with HTML for the button/link, which just checks for a URL parameter and deletes the transient if present.
But I’ll make sure to remember this thread for later use.
