how to maintain top level reference when creating independent copy of subassembly?

Hello,

I'm trying to make an independent copy of sub assembly "Assem1" without breaking top level references. See example below:

I've tried doing this using several different methods and always end up with broken references. Can anyone provide a solution?

Here is an example of a method I tried. First I make a copy of Assem1 with copy and paste:

Then I try to make the Assem1<3> copy independent by right clicking on the assembly and choosing "make independent". I am presented with a save dialogue. After giving the part a new name and clicking save, I get a warning that the references will be broken. It tells me to use the 'references' box to fix this, however there isn't  a references box:

Any thoughts on a solution to this problem? This problem has caused a lot of headache for me when using top down assembly design.

Best regards,

Kevin

SolidworksAssemblies