>>531941792
well, I'd still try to fix them in there
though making the new image 4096x4096 won't be too bad

I have Gimp 2.9 becuase I've never needed to upgrade it and I have all my plugin shit setup already, so yours may be newer and its layout different

but to setup grid just go to Image-->Configure Grid
>see pic

then to activate/deactivate grid, its just View--> show grid
ticked or not ticked
yes its by pixels