Hello @j4k3
You can edit placed, posed Nanos in zero space with Symmetry via the Edit Mesh function in the Nanomesh Palette. This will only affect the nanos in the active subtool.
You cannot place Nanos on any other subtool but the active one. So you would have to place the Nanos in turn on each subtool, or create a new, merged version of the desired subtools, for instance with the “Merge visible” function in the subtool palette. You could then place Nanos simultaneously on all the meshes in that subtool.
Transpose Master is a plugin which lets you quickly create a merged, low poly version of multiple subtools with multiple subdivision levels, pose that merged version, then transfer the changes back to all the original subtools at high resolution. You could use this to quickly create a low poly version of a tool for preview and posing. You can place Nanos on this tool to see how they look, but you cannot convert them to geometry and still have the tool able to transfer the changes back. The topology needs to be unchanged.
You can copy and paste the settings between Nanos applied on different subtools with the Copy and Paste functions in the Nanomesh palette.
Good luck! 