This is really a lil-gui question more than a Three.js question. Apologies if asking in the wrong place, but where would be the right place?
I am upgrading my Three.js version and getting lil-gui along with it instead of dat.gui. Previously, when using dat.gui, I needed to set a variable whenever a gui folder was opened and unset that variable when the folder was closed. I accomplished that by using Common.extend to override the open() and close() methods in dat.gui.module.js.
But there is no Common in lil-gui, so is there a way to override open() and close()? Doing so may be complicated by Three.js including only lil-gui.module.min.js instead of the complete module.js.