"Set as default" button not working

[Hurdet]

In the config dialog "Edit file type" of "internal Associations...", the "Set as default" button doesn't seem to work, it always stays disabled.
Button reference is also missing in help file.

[petermad]

2Hurdet
I guess this is because this dialog is also used by "Associate With" -> "Edit type". When used in this context the Help for the button is shown