Hello !
I don’t know how if it can be done inside a static mesh, but you can make a blueprint.
Import your static mesh, the floor plane in this case, and in Unreal Content Browser right click and create a Blueprint Class, and choose “Actor Class”.
Inside the Blueprint put your Static Mesh and drag a Decal Actor.
Then, everytime you want your asset with the Decal use the Blueprint created.
Although it is not the most optimized solution really, since if you want an object that is repeated X times and has a same detail in each part, the best thing to do is put it in the texture.
I hope it helps you!