Synthesia Metadata Editor 1.4.0
This is a pretty small update. Really, just getting the tools to turn over again after another seven years was the hardest part. (I guess Xamarin for Mac is going end-of-life in a couple months? That will make this even harder next time.)
It's a little late to the party, but now you can add MusicXML (.musicxml, .mxl, and .xml) files to the song list. This took a little more effort than it sounds: the tool already loaded .xml files as Synthesia metadata files themselves. Since day one it has treated .xml as an unofficial alternative to the .synthesia extension. So now it has to do a little disambiguation when you drag in a single .xml file and check to see which of the two--an actual song or just a metadata file--it might be.
There are one or two other small fixes and now it's a "Universal" macOS app. And that's about it.
Download the latest Synthesia Metadata Editor release at GitHub.