Change default folder for screenshot

Hi,

I am using an Inkpad X (that, if I understand well, has almost the same software that the Inkpad 3) and I would like to change the default folder of the screenshot to a folder in "Dropbox Pocketbook" in order to direclty synchronise the screenshot with my dropbox account.

I tried to use "ln -s" to replace the screen folder to a symbolic link in order to accomplish my goal, but it seems that I doesn't have the authorisation for that (even in root in my manjaro linux).

Any advice? Thanks for your reading!