I had a custom tag on versions previous to 5.6 and worked without any problem:
I could see the inspector in the template selector with my custom tag so I could set my value and then when published get that tag replaced with the actual value.
In 5.6 it prints the %UNITY_CUSTOM_MY_VAR% literal as it is. If it helps, my custom tag is inside a JavaScript string like this: var a = new MyClass(“Test %UNITY_CUSTOM_MY_VAR%”);
I think that it doesn’t matter where it is because I suppose that Unity only replace content of that file with a simple replace.
Sorry for not posting it earlier. I have created a simple repro project duplicating the “Default” Unity template and adding a custom variable.
Case 904373
Also related to this (but it’s another unrelated bug) if I remember well if you have a custom variable and you switch to other template and then switch back to the previous one it persisted the values and now it clears them.