Unable to change the user interface in master docs

Hi, for some reason when editing a master doc (.odm) I can’t change the user interface style, while in a normal document it works. I’ve tried this on v.7.0 and v.6.4.

Is this an intended behaviour or what is going on?

regular .odt file

regular .odt file

.odm file with no 'user interface' option

.odm file with no ‘user interface’ option

(“touched” by ajlittoz but unchanged because the screenshots wouldn’t display on my computer)

I can add User Interface menu with Tools>Customize but it displays disabled (greyed out) without the submenu in an .odm.

I don’t see reasons why the menu should be forbidden in a master document, apart from the fact you don’t really format a master but mainly link to other subdocuments. There is a still some content specific to the master which can receive formatting and styles won’t do everything. So menus are needed and therefore they should be able to presented in the user preferred interface.