Modeling mode, is it possible to project UV locally ?

So, I’m working on a game with a very squarish environment and because of this I decided to use the build it modeling tool to make the entire level as a single mesh to make it easy to edit and adjust on the go, but I have one issue :
I need to edit certain faces to match the texture on certain areas, and also need to reproject certains new/modified areas, using the UVs > Project function. Except said function seems to apply to the entire mesh with no way to select the area you want to generate a new UV for (unlike MatEd for example, that let you paint where you want to do the change). It would be very useful to have the option to paint a certain area, and project a new UV only for said area.

I know I could use different meshes for each individual surfaces as a workaround, bit it would make everything more harder to work with and sounds like a dirty workflow.

But maybe I just don’t understand how it works, so I wonder if this is really how it works, of if there is a solution to this problem.

I think you’re going against the UE UV grain there…

You can paint other textures on parts of meshes ( vertex paint ), you can isolate certain areas to use different textures by editing the UV map. But it’s a LOT easier to use separate meshes.