I know that MU does have some sort of a way showing when a manga(novel) appears on the releases, but

I often browese the Genres & use Categories/Tags. something that would be appreciated, novel as a genre so when we search for manga we can turn it off or on, to find novel manga or exclude it.

You can already do that.

Go to advance genre search, then scroll down and choose "Only show results for "Novel""

Yes i do know that. but you can't remove it, almost all (TYPE) can't be removed it's either all or just search 1 of them
except doujinshi due to the genre
can there be a, don't show novel's? as there is for "show only". or where you can pick, like in the genre section?