I'm creating a Super Mario level editor, would it be considered as a "remake" of SMM?

[Luigibonus]

I don't believe making a Mario fan game with a level editor automatically makes it a Super Mario Maker clone. I am the creator of Super Mario Construct which is also a Mario level designer, but it's got a much different philosophy. SMM focuses mainly on ease-of-use by keeping the amount of content simple and small to cater to casual level designers, but this goes at the cost of introducing a lot of limits to what the level designer can do.

Meanwhile most Mario fan-editors out there are vastly different in that regard, they're more expansive and you have much more freedom with what you can do with your levels, but that comes at a cost of the level editor having a bit of a learning curve.

There are some Mario fan-editors that do intentionally try to mimic the appeal of Super Mario Maker though, intentionally making the UI similar and branding themselves as a PC Mario Maker. That's fine by me, but I would recommend staying clear of that direction since there are already a lot of SMM fangames out there.