Hi Pepijn,
no havn´t tried it yet. i´m the guy who has at least 2 screws und 3 springs on the table after setting some technical stuff back together so i have to build up some confidence 
but i found this video: How to change cables shimano ultegra 6800 shifters - YouTube showing how to set up the lever shifter
and i think it must be the same procedure with the cable of the dropper post. maybe i give it a try the next weeks 