I wasn't really sure how to call this kind of form element. I was trying to get a Grid within a Tab of my module but then I stumbled across the
'Customer->Manage Customers->Add Customer->Addresses'
form, more specifically the 'Add New Address' tab which would work perfect for my module. I'm looking at the core files right now but I'm not experienced enough to separate the needed code from all the (for me) unnecessary stuff. I hope somebody can give me a hint on what is needed to accomplish something like this or a link to a tutorial/overview (I couldn't find anything). I already have a working Grid, I only need to add a tab with similar functionality like explained above.