First off, it's amazing.  100%.

I'm a little confused by the tool, though.  I'm in a multi-extension workspace that I have lots of pre-existing code in.  I open a CustomerCard page extension object from one of them.  I get the phenominal layout, overview, all that.  I can see what fields are added by what extensions.  Just.  Wowsers.

But, I drag two fields onto the card, one a base and one an extension field.  I drag around a few others.   ... How do I save those changes without hitting "Run"?   How do I decide which extension should hold that code?