Selection Utilities provides a series of utilities for manipulating, saving and creating both single and multiple selections, many of which are inspired by Kakoune.
To start learning and using Selection Utilities you can use Master Key, as Selection Utilities was designed as a modular component to support Master Key. Master Key has extensive features that make these commands easily discoverable.
Because there are so many commands, and any given set of keybindings for this extension could easily overwrite existing bindings, there are no default keybindings; if you do not want to use this extension via Master Key, you will need to learn about the commands you want to use and then customize them yourself for your own purpose.