Best way to lay out sub elements in a table

I have a table that lists network switches. The headers are Model, Stack Size, and Modules. If the stack size is greater than 1, I want to be able to add the additional stack members under the lead member and select different models and modules for each stack member. I also want to be able to add rows to the table to add additional lead switches (and their subsequent stack members). In the end, when I hit submit, I need to be able to pull data on the lead switch as well as all the members.

I already have this coded to configure a single lead device and add additional lead devices with a button. I just don't know what is the best way to add the member devices and distinguish between lead and member devices.

What is the best way to accomplish this? Nested tables? Tree grids? Something else? Would want it to look something like this:

Lead Switch Model          Stack Size         Module
---> Stack Member                             Module
---> Stack Member                             Module
Lead Switch Model          Stack Size         Module
---> Stack Member                             Module

This is what I have now...