Removing routing !!!!

And achieve what?

In menu remove Assignments, I would like to remove only the Routing Assignment !!!!

I'm not sure, what you exactly mean with routing assignment, because it's no Quartus category in my opinion. To remove all compilation results, you can simply delete the db directory. Other specific assignments (beside pin location assignments) are accessible in the Assignment Editor tool and can be e.g. deleted there, if required.

Can you tell us specifically which assignments you're seeing in the project that you want to remove?