Real-time shadow maps, tell unity when to render from lights

I'm not sure how to ask this question, basically I want to be able to control when real-time shadow maps are updated.

For example we have a scene with a room, that has multiple lights that we want to bake, all good so far, we can bake it no problem (The lights don't move or anything like that)...

Then say we add a chair or something similar, we can't have the chair as part of the baked lighting, because the chair could be in a different location. It's unlikely to move during a particular run of our application and the application itself is WebGL so multiple real-time lights that are updated every frame are not possible.

So how do we get Unity to only re-render the real-time shadow maps when we want them to, rather than every single frame? So in our example we would tell Unity to render the real-time shadow maps at the beginning (or lets say when the chair is added to the scene), then we just want to re-use this rendered shadow map for the entirety of the run, unless something else that is dynamic is added.

Please say this is possible in Unity, seems like a simple thing I could otherwise implement in my own application.

P.S. I am using URP so maybe it is something that can be done though that?