Abnormal parking space regulation - legal action or ignore?

Yes, links are forbidden here (nach extern). But you can set a search term combination that leads to the destination in the world's largest search engine...

and that parking spaces in front of the garage are not recognized regardless of size

I agree with the municipality, in the case of confined parking spaces, that is at least correct. There are also some municipalities that allow a second confined parking space for the same residential unit.

We don’t want to clutter the garden with parking spaces that are never used.

You probably just want to clutter the city treasury with the buyout fee :)

In principle, I could provide a link, but I read during account creation that posting links is prohibited and leads to account deletion...

Yep, that leads to warnings. But you can mention the name - Bebauungsplan Otterndorf Baugebiet Grüne Wiese or similar. Or write: stellplatzsatzung minus otterndorf punkt de

I would probably create a gravel area bordered by shrubs and grasses (keyword prairie garden) that has "accidentally" overgrown due to disuse and has turned into a little bee paradise. No one can seriously expect in 3 or 4 years to drive away the bees and create a sealed paved surface that is not needed. No lawyer is needed then; a call to the daily newspaper will do.

A Google search for "stellplatzsatzung stegaurach" should find the document dated 26.03.2012 with amendments from 29.11.2016.

Hit. It works with the search engine after all.

The SP must be secured.

You can calculate the replacement value.