Hey Mike, 

If you have the Glass Catalogs loaded in the System Explorer, you can just separate the catalogs you want to substitute from with a space.  The following Glass Substitution will search in both Schott and Corning catalogs:

Although a checkbox might be nice from a GUI standpoint, I think to keep the GUI consistent with the ZPL and ZOS-API, separating catalogs is the better option.

Hi @Mike.Jones,

I think @John.Hygelund was also making suggestions in that direction in this post:

Not to say that there doesn’t need to be imrpovements to the glass catalogs (I actually think all catalogs would benefit from some rework, particularly to search an item based on its product number) but perhaps you also find something interesting readily available there.

Take care,

David