We are finally (after a couple of months of significant effort) at the point where we can release 1.4 of the library, this version will include visibility, that works both locally on the menu and remotely.
TcMenuLib - the library itself has now got support for this on master, and the UI's will be following along very shortly, probably within a week or so.
In terms of enabled status: There is already a method of making something non-editable, set the read-only flag. In a future version, we could give the option of a different rending color for this.
Limitations:
If you change the visibility of an item after the display has been initialized (think after setupMenu() in setup), you must completely refresh the menuMgr by calling setCurrentMenu() with whatever menu you want to display (or the root menu). See the examples, keyboard ethernet and Ada32 Ethernet have been updated with this support. Also, the changes will only take effect remotely after a new remote connection.
Edit - link to tcMenuLib:
https://github.com/davetcc/tcMenuLib