I am trying to delineate wetlands using satellite imagery in QGIS 2.10.1-Pisa.
I'm using the Freehand Editing plugin.
Is there a way to draw polygons without having to hold down the mouse button, like you can with the freehand tool in ArcMap?
As far as I know, there is no such setting, but you could open a feature request on the plugin's bug tracker asking for this option.
You can map the mouse button to a keyboard button using X-Mouse Button Control
I haven't tried the above suggestion yet, but you can create lines in Google Earth by holding down the mouse button (works pretty decent with a touchscreen too!) then save as kml/kmz and import into QGIS that way. It has its limitations but it's a quick fix.
Edit: Apparently I misread the original question, but I'm leaving my suggestion up because it might help somebody somewhere at some time.