Quick switch is a VL (virtual Library) term. That says you have 1 REAL Library.
You simply need to determine what each VL expects (OS independent) as its 'filter' values.

right click the VL's tab: Edit... (remember to CANCEL if you make no changes)
OTOH you
imply a different structure OF FILES. This IS NOT changeable for a CALIBRE Library. You could have a template for a DEVICE (send to...), but that does not change the real Library layout