I assumed this must be a known issue, thus the light job on clarity. Sorry. Additional info...
When initially getting the 4.7.3 apps installed, I was notified of the unidentified developer and used the "open anyway" option in SysPrefs to launch. I did not modify the system to show the "open from anywhere" choice.
SE, SC, and SCPlayer all launch and work. SM launches, and successfully shows the initial selection to choose Build or Prepare or Open. All of the three choices succeed at moving from that window to a new one before throwing the same SuperTalk Error Number 64: Can't find menu item. When attempting to Open an Existing Congfiguration, the SuperTalk error was only presented after I was able to choose the config file successfully. When I choose Build or Open, the fatal dialog is in front of the SM window in which the build setup occurs. For Prepare, the underlying window is the one with only "Build" and the option to set the project or player document.
Some new, maybe more useful information - when I booted the system today there were "recovered items" in the trash, which was empty yesterday. There were 4 files, all password protected SC documents with only numeric names, non sequential. It seems SaM was at least able to make it through some of the process before needing a menu item. Although these projects are locked, there is a QuickLook preview. This reveals that SaM was able to open my existing configuration file, populate the source and destination path, read my icon file, and populate the icon well with a preview of the app icon.
This boot drive was prepared in the past few days with the Sierra installer on the app store - macOS Sierra version 10.12.4, with no available software updates. Booted on a mac mini 2.5GHx i5 with 16GB memory.