popup with a list of shortcuts, organized in nested groups?

[xuanswe]

Is there a shortcut to show a popup which lists all shortcuts in nested groups mentioned in the README.md.

Like Ctrl-U / U, which lists some groups of actions, select a group will show a nested list of actions.

Now, for example, it would be nice if we could have a shortcut to open a list like this:

Then, if we select item "Ctrl/Cmd+L (line) - manipulate code lines" in the popup, we will get another popup like this:

PS: I know we can open a PDF, but that's not convenient.