What is the use of NoCallback?

You have to understand that this is an open-source product, you are able to use it freely under the terms of a very lenient license.

However, the flip side of that is that sometimes the documentation may not meet your needs, or there will be something missing.

We actually try to keep the documentation as current as we can and don't take new versions out of BETA until at least basic docs are in place.

However, in this case, the NoCallback value had not been documented, but it's been there since the very first version! I've added it to the menu item type documentation today. There is a link to documentation for each menu item on the top of the UI, this takes you to a page for that type, and the documentation relevant to all menu items is linked from there.

https://www.thecoderscorner.com/products/arduino-libraries/tc-menu/menu-item-types/#callback-function-for-changes

As I said in the other topic, if you can think of how it could be better arranged, or if there is something simple we can do that links it up better, we'd welcome the feedback.