I already put in a ticket and got the answer this is currently not possible, but was encouraged to put in a post here to hopefully being integrated one day.
In my situation we have a huge list of project names (and constantly growing) that we'd like to be able to pick from in a from related to a SmartSheet. We find that updating the column properties as a picklist is very cumbersome and has to be done for several SmartSheets constantly and is not very user friendly. So being able to link a certain column options to a source sheet, that then comes up in the form feeding into the SmartSheet as picklist would be very useful.
Unless somebody already knows how to do that in some way, it would be great to have that option eventually. Thank you.