I was in a cleaning mood the other day and while scanning through my hard drive I saw a ton of files that I realized belonged to old Dashboard widgets that I no longer use.
Scrollback was gone along with the path and surprisingly there is no “remove widget” feature available in Dashboard, only one to get more of them.
So for future reference, widgets get installed either in
/Library/Widgets or in
~/Library/Widgets. (~ is the unix shorthand for the current users home directory, so in my case /Users/henrik)
Removing just six old widgets I got rid of 9772 files occupying 76MB in total so in my opinion it was well worth the few seconds it took me to delete them, YMMV though.