Thank you, Walter (?). I appreciate the suggestion. I was aware of that tool, and that I could do all the required edits and "customization" manually.
However, I don't want to do that, because that would imply requiring Users to replicate my attempts to "automate" tasks for a custom build (Ubuntu-Server + MATE Desktop + reduced User-selected set of Apps), then I will have to abandon the attempt to come up with at UbuntuMATE-like alternate that could step in if UbuntuMATE were to become "frozen", as a flavour, for lack of development.
Under UbuntuMATE, the process would somehow automatically add a missing category, then deposit the App-specific launcher in the required menu "slot".
I'm trying to find the specific mechanism I need to install as the first Application after the server OS base followed by the MATE Desktop install.