In SMILE GAME BUILDER, it’s possible to use default keys for other purposes, such as Dash. However, there is no functionality to use other keys, so there’s often a trade-off and that key’s functionality needs to be sacrificed to use it.
AmalgamAsh‘s tutorial demonstrates how you can repurpose them to "bring up User Interface elements” and to use the double-press function to call "a custom menu that you designed" without needing to sacrifice keys.
The tutorial is conveniently available to view on Google Docs, along with images to make things easy.
I won’t directly port this here for that reason, but you can view the document and follow along.