For those bass stabs:
in the voicing tab: put it on 'monorotate' and 'legato triller'
than in you piano roll, make low note (to where you want your bass to drop) overlap the note where you want that stab/slide to happen (kinda hard to explain, I can take a screenshot if you want)
then, in massive, go to the osc tab and play around with that 'time' wheel. how more you turn it clockwise, the slower the bass will slide between notes.
Play around with that wheel a bit and voila.