Need the code for customization sidebar

Hi,
I’m looking for code for a sidebar where the content (images) on the page that contains the sidebar expand or contract depending on the whether the sidebar is open or collapsed as happens in the Preview of the twenty twenty-one WordPress theme .
Any code or pointer to code that achieves this would be very much appreciated.

Thanks

• This topic was modified 4 months, 2 weeks ago by blogdropper.
• This topic was modified 4 months, 2 weeks ago by blogdropper.

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