I change this but does not have any effect and when I quit mypaint I check and the value has been reverted to F11 by itself.
# Recent gtk versions don't allow changing those menu shortcuts by # default. <rant>Sigh. This very useful feature used to be the # default behaviour even in the GIMP some time ago. I guess # assigning a keyboard shortcut without a complicated dialog # clicking marathon must have totally upset the people coming from # windows.</rant>.