But you can set the "inherits from template" property of the design elements.
In our case we have a kind of master template (assRepository), every application template inherits from. In the application templates (e. g. assPassword-Safe) changes and new design elements are marked as "don't overwrite from template". Then the applications inherit the design from their respective application.
Then we have customer master templates (customerNameReplository), which inherits from assRepository and has some modified design elements (like the customer logo).
And finally there are customer application templates (customerPassword-Safe), which would have to inherit the application specific design elements from the assPassword-Safe template and other customer specific design elements from customerNameRepository. But this is not possible.
We decided: customerPassword-Safe template generally inherits its design from assPassword-Safe template, but some specific design elements are inherited from customerNameRepository.
This way, when we add new design elements to assPassword-Safe template they are automatically added to customerPassword-Safe, but if we add new design elements to customerNameRepository, we have to add them to customerPassword-Safe manually.
"load design -f ..." or a manual design refresh in the Notes client work as expected.
Design inheritance on database level is way faster than on design element level.