When creating a custom template in Qt's designer (File->CreateTemplate) i always get an error "Can't create template". I've looked after it and found the answer in the qt ebuild (not in any particular version, it applies to all of them). There is something missing in it. Qt designer stores it's templates in the directory (got this from the source) $(QTDIR)/tools/designer/templates/ This directory is usaually empty as long nobody creates a custom template. But it is not created by the ebuild, that's the reason why designer reports the error "Can't create template". I've created this directory by hand and now creating custom templates works. Thus the qt ebuilds need to be extended to create the stated directory.
This directory is now created by the ebuild.
