This is now done - FEATURE: Allow admins to localize custom sidebar section and links - Pull Request #41795 - discourse/discourse - GitHub
Some screenshots:
Will be updating the main docs as well.
I’ll be closing this topic on a timer. Please feel free to create a new topic for any follow ups or feedback once this is closed.
EDIT: small follow up PR here for community section: FIX: Allow manual Community sidebar links to be localized - Pull Request #41898 - discourse/discourse - GitHub