I'd like to keep my sketches on OneDrive but since I hit several problems (maybe with libraries being in different states or the single installations assuming different states - whatever) I'd like to keep the libraries separate / local on each device but I did not find a way to do that. Is there?
Libraries must be installed to the "libraries" subfolder of the sketchbook folder. So we know that the sketchbook folder must be on your local drive.
Fortunately the Arduino IDE is more flexible when it comes to sketches. Although the sketchbook is a convenient place to store sketches, you are welcome to store them anywhere you like.
So use the sketchbook folder solely as a place to store libraries on your local drive and store your sketches to any path you like in OneDrive.
Thanks! Will try that