Story #69712: Further FormEngine development
TCA: Palettes in "subtypes_addlist" are not processed
I'm using `subtypes_addlist` to show additional fields for certain subtypes.
This works fine except if I try to use palettes there. They seem to be ignored and don't show up in the backend.
Interestingly, an exception to this is when the same field is shown elsewhere in the type's `showitem`. In this case the field will be shown in the regular `showitem` and in the subtype palette (which is generally not desired).