Missing shortcuts for grouping of images

Is your feature request related to a problem? Please describe.
I often switch between images in a group, and switch the image marked as leader. In order to save screen real estate and reduce the need for me to use my mouse I'd like to be able to do this with keyboard shortcuts. So far, I only saw the option to expand/collapse all images.

Describe the solution you'd like
Add the option to add shortcuts for the following actions:

• Expand/collapse the current selected group
• Mark the currently selected image as leader of the group

Additional context
This doesn't seem like a lot of work to add, as there are already many functions already have the option to add shortcuts and this isn't adding any new actions. I do have quite a bit of programming experience myself and if nobody wants to do this I could do it myself, but that would probably require quite a bit more effort as I am not familiar with the codebase.

Start by tracing the existing keyboard-shortcut entry point for expanding or collapsing all images, then locate the actions for changing the group leader. Add configurable shortcuts for expanding or collapsing the selected group and marking the selected image as leader, and verify both actions work from the keyboard.