When loading our plugin for FileMaker on MacOS 10.15 Catalina, you may have seen such a dialog.
We now made a notarized version of the download: MBSFMPlugin93-notarized.dmg
This plugin download is notarized. But it misses the iOS parts as you can't have currently iOS frameworks in Mac software notarized.
We hope to be able to notarize all downloads in the future for our 9.4 release to avoid friction.