Factorio Forums

As title suggests: I think it makes more sense that copy/paste can add a module inventory request when pasting into a existing machine. Otherwise we have to remove a whole bunch of machines together and paste the machine with module slots again.

Also:

I hope upgrade planner can add a support to insert empty slots with specific modules. (A possible implementation: you could achieve this by regarding "empty module" as another type of module. With this, in additional to insert empty slots, players can also remove unwanted modules from machines)

Please have a look at https://mods.factorio.com/mod/ModuleInserter
I think, this is more or less, how it should work.