I've been working in Unity for awhile but I'm pretty new to making my own models. I'm using Blender since it seems like a pretty good tool for the job. Let's say I am making a simple scene in Unity with a table that has a cup and plate on it and some chairs. Assume I want to be able to move each of these objects around independently from the other objects. Does this mean that when modeling in Blender, I have to model each object individually and import them separately in Unity? It would be nice sometimes to be able to model entire scenes in Blender, but if stuff in the scene isn't intended to be static, then there is no way to treat parts of these scene as objects and manipulate them individually in Unity right?
Yes, if you don't want to deal with more complex stuff in Unity instead.
You don't really have to make them separate models, but you would have to separate their meshes inside Unity itself. This will involve much more effort on your side than just making them separately in Blender, or exporting the scene part by part (i.e. export a chair by copying and pasting that into a new model).
This way, you won't have to deal with splitting a mesh in Unity and moving things around that way.
In short, it's not impossible to do a whole scene in Blender then export that into Unity and move stuff around individually, but it's really hecking hard to do so. (Side note: you might also need to use some other assets from the asset store and maybe even some stuff that will cost money.)