Toggle features

[rsHalford]

This may be more useful when certain feature requests currently being worked on for core, become available. But I'd think it would be nice to have the ability to toggle certain UI elements, such as white-space indicators, file/symbol tree, a future terminal buffer?, etc.

Each toggle could either be a key bind set by the user, or set to a mode mapping like space + t, to get a list of potential toggle options.

Open to knowing other people's solutions to quickly performing these tasks.