I'm sure I'm missing something basic here so apologies if this is a very stupid question, but how do I copy a subassembly in library designer?

At last week's Innergy conference I was convinced to finally give the foundation library a go. One thing that was repeated was to make a copy of the 2D Instructions subassembly so that your organization's changes aren't overwritten with updates.

I am brand new to library designer, but I did read a few knowledge base articles, and I found the copy subassembly button and... it's greyed out. What am I missing?