So what I want is only the current category, not the full path on the category page.
I did not find a setting for that?
Sadly, Magento 2 does not offer an option to "shorten" category URLs.
However, this solution might help you achieve your goal.
Otherwise, in case you don't like working manually using the above solution, there are plenty of third-party extensions out there that does this job. Simply google "Magento 2 short (or unique) category URL", you'll find a bunch of them.