The specified #ajax callback is empty or not callable

Got the same issue, but after a page refresh, token is selected and the "Pattern for the SKU" text field appears.

Yeah, got the same issue. Just save it, regardless of the error and then reload the page... the token field will show up after that.

I got the same issue, the comments here encouraged me to try regardless so I saved the page and everything worked!

I can also confirm this is broken in the latest release!

So turns out the ajax callback was never implemented. Had some time to look into it and opened an MR. To test:

1. Create a new product variation
2. Configure the automatic SKU
3. When you click on the plugin, see that there's no error
4. Also see that the selected plugin form element appears

While I did not review the proposed fix line by line, I can confirm it is working as expected to fix this annoying issue.

Thank you very much!