The On-Screen popup for keyboard shortcuts is currently limited to:
General / Global Shortcuts
Page / Blog Post Actions
Editor - Block Formatting
Editor - Rich Formatting
Editor - Editing Actions
Editor Autoformatting - Font Formatting
Editor Autoformatting - Tables
Editor Autoformatting - Emoticons
Editor Autoformatting - Autocomplete
Editor Autoformatting - Styles
Editor Autoformatting - Lists
Their is also a "View All Shortcuts" that redirect to https://confluence.atlassian.com/get-started-with-confluence-cloud/keyboard-shortcuts-934720180.html
But THAT page includes the statement "We could give you a list here, but then you'd need to keep referring to this page."... Which is kinda the point of the help-screen redirecting to THAT page!
Maybe THIS is a place that we can help Atlassian out and fully list ALL of their keyboard shortcuts.
By the way,
https://jira.atlassian.com/browse/CONFCLOUD-66529 -- is a "Suggestion" that the documentation of the keyboard shortcuts actually matches what the app does (Atlassian doesn't want to mark any documentation errors as actual Bugs!)
https://jira.atlassian.com/browse/CONFCLOUD-66530 -- Is another "Suggestion" for Atlassian to make the keyboard shortcuts actually work as documented!
Here is a JQL query of the shortcut-related issues: