NSEU - assuming you mean an actual DME step down rather than DME/altitude tables on an approach, yes, it can be programmed into a 'glass cockpit', but generally there will be an 'imaginary glidepath' that can be flown for the approach, sometimes meaning you may pass somewhat above a particular (early) 'check height' (but not, of course, below). These step downs normally only occur where terrain makes the approach angle too steep initially for a 'normal' approach.
Yes, PNF will call the checks and of course PF will be aware of them. Only by 'mutual agreement' should a block altitude be left for lower at the appropriate DME.
NB As with all things in life, para 1 will have its exceptions and I expect someone will come along with one soon.
