I don't fly the 320, but do fly an all EFIS, FMS driven aircraft.
On nearly all the routes we fly, the arrival is generally a radar vectored ILS approach. The FMS will generally be programmed for either the full procedure, or 'tidied up' to something approximating the path flown on vectors - though it can't be used for NAV legally in such a case. For example, you might have the arrival hold programmed in, and a 'direct' track onward to the centre fix of the approach.
A more correct way of doing this would be to leave the procedure in place as the active plan, and once receiving vectors for final approach path then extend the final approach path outwards. This will clean up the screen, leaving only a magenta line representing the final approach path.
On my current type, an added benefit to this method is a display of lateral offset of final approach path, really useful for non-precision approaches where we currently are not permitted to use RNAV.
Some other systems call this extended centreline an 'intercept' or a Pseudo VOR, PVOR.
Hope this helps, but sounds like what you were after