There are several things WRONG with your plan 1) roots exposed to the air will dry out & die 2) there is a "up: & a "down" to the stem & if the stem (cutting) is stuck "up-side down" then it will not root. 3) the foliage if placed in water will soon rot etc.....
Since there are at least 4 species that have members called "umbrella plant" I will asume you mean a Schefflera spp. then take a cutting remove all but 1 leaf & then cut that leaf in half... apply 0.1% IBA (rooting hormone ) stick in well drained soil & mist taking 20-50 days to root.