If you use a lot of UCS's try this. (great for 3D work)
Instead of saving/recalling a UCS, it is easier to insert a text label in the drawing for each UCS.
While in the UCS you want to save, Use DT (dynamic text) to place a text label anchored at the origin.
Anytime you want to recall that UCS use a keyboard shortcut to align the ucs with that text entity:
(DEFUN C:uu () (COMMAND "UCS" "E")) ; Align ucs with entity
I usually copy the text into any layer that I might use it from.
An added advantage is that when I copy and insert these layers into a new drawing, the text (and therefore the UCS's) get inserted too.
Bill