@Matt Liberty Is these a easy way to constrain the tool to place group of cells in small region with-in floor plan?. Background: I like control control clock skew cells near to PAD in each MACRO, but these cells are scattered in floor plan and it's creating different delay in each MACRO.

Not really. We have some work that will land soon for hard regions to be used for power domains. This sounds more like soft region. You are free to pre-place instances yourself as a workaround.