I'm working in Blender 2.93 Alpha (more details if needed), and I'm looking for a way to apply a solidify modifier to only a specific vertex group. However, I can't figure out how to assign pieces of my geometry node group to the vertex group.
I may have misunderstood the question, but as I understand it you could use an attribute mix node with the factor being the vertex group, and the inputs being the different "branches" of the node network you want applying. In this example I mix two sets of points, one from a scaled up sphere and one from the original vertex position. For the solidify modifier you can just use the vertex group input, with a group. Sorry if I misunderstood the question.