Hi there,
At the moment this is not implemented in the core but we do plan to support it. Two options for right now:
* you could try locally modifying the EnumMenuItem to handle this for now, but the designer wouldn't be able to work with that item. However, you can add items into a menu yourself at runtime, a menu list is nothing more than a linked list (where each menu item has a next pointer).
* My favoured approach would be to implement it as a editable RuntimeMenuItem, these are quite new so the documentation is not great, but the reference implementations in RuntimeMenuItem.cpp/.h should point you in the right direction. Again as above, you'd just add this custom menu item into the linked list at the right place in code.
This may suffice for you in the immediate/short term, while we get around to this feature. You'll even see how to add extra menu items at runtime in the packaged esp8266 example.
As I said above, we have a plan to add it, as in the longer term we need it ourselves for a few projects. However, at the moment we are on a stability drive, the last two releases have introduced bugs onto some of the platforms, as there have been a few huge changes introduced (RTOS support, multi-core safe task manager). We need a couple of cycles where there are no new major features. But we'll add it to the 1.7 issues.
May I ask that you add an issue into
https://github.com/davetcc/tcMenuLib/issues with the information about how you see it working, and I'll combine with our existing thoughts on it.
So for now, you could do as suggested above, and add a menu item yourself with my preference being a editable runtime menu item.