ATM, there doesn't appear to be any way of doing this, without this long-winded process:
1) Select elements to add
2) Choose the stored selection and [+] it to the current
3) Rename the stored selection, to Copy the name,
4) Delete the stored selection
5) Add Selection, pasting the name copied earlier.
Phew.
How about an easier [Add current selection to selected stored selection] button?
Unless I'm missing something?
