slug translation

One more ??

With a reference to this question which might not include the final conclusion: https://www.ads-software.com/support/topic/custom-post-type-dynamic-slug-404/

Dennis says, at the end (referring to the inactive input fields below ‘Rewrites Settings’ in the settings of MSLS):
“These fields are meant for this kind of problem. Do the values differ when you switch between the languages in the dashboard?”

In my install the values of these fields do not differ between the two sites representing the two languages. Both are in english and originate from the name/string i use in ‘register_post_type(‘THISSTRING’, $args);’ to create a custrom post type.

Is there a way to edit these fields/the content of these fields?
Make them german for one site and keep english for the other?
Maybe directly in the database? Would that break something?
Or is the solution with the filter function (which will work, of course) the best advice?

Thanks a LOT.