When changing the Size of a page in Page Details under Page Settings, I would like to be able to choose which edge(s) of the page (left/right/top/bottom/both/all) the cells/pixels are added to or subtracted from. I believe that at present the new area(s) just add to the right and/or bottom. If more space is needed to the top and/or left, I've got to then move everything on the token layer, move everything on the GM layer, move everything on the dynamic lighting layer, reset the explorable darkness, then manually reveal previously explored areas. I've yet to run into a situation where I want to make a page smaller, but I expect the dimension change similarly effects the right and/or bottom edge(s) only.
