Wood filler is often used as a term describing all sorts of filling agents, including wood putty, but also epoxy fillers, acrylic fillers ... shouldn't be used outdoors because it can shrink and crack ...

Epoxy wood fillers ... Because it doesn’t harden like wood filler, wood putty won’t shrink or crack, but you can’t sand it.

Clean out any debris from the crack in the window, and fill it with wood filler or epoxy. Allow the solution to overfill slightly. Once the filler dries completely, sand it smooth. If your window ...