Channel Packer Pro is a Unity editor tool we made to speed up our workflow when making our first game. It started out as a basic tool that could pack textures in a fast and convenient way while working in the Unity editor. Since then it's had some big changes that allows the user to generate, post process and pack images within the tool itself and is even capable of converting the textures of an entire project. This makes it really easy to switch between render pipelines in Unity so the textures are compatible with the shaders and it could even be used to migrate your project to or from a different game engine.
Channel packing is a technique used to save on texture memory and reduce processing by combining multiple textures into one.