Tell me more!?!?!? This sounds like an amazing thing — all my graphics, etc... are stored infolders, but doe you mean a specific project type? Or just using folders? That would be great, Could I duplicate the animation, then just swap out the graphics in the copy?
He means if you are saving your project as a folder project instead of capx (in the file menu it's something like project), then you can go to wherever you are saving your construct game and see all the files. They're in the "animations" folder. So in C2, right click on the file/sprite you wante duplicated (not in the image editor, the actual sprite on a C2 layout or in the file browser) and select duplicate type. And I apologize for not being near C2 at the moment so my terminology may be off.
Then you can go into the animations folder (the one made by C2), go to that new duplicate, and copy-paste replace the frames you want to replace. C2 will read those new graphic files but it won't go through the import process so the collision polygon will remain. So you'll still have to set the polygon at least once, but for subsequent variations, it goes much faster.
Hopefully that all made sense.