Why is my theme editor showing a narrow view on desktop?

Store Design
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Topic summary

  • Issue: In the Shopify theme editor, the desktop preview suddenly collapsed to a very narrow view.
  • Impact: The user cannot restore the normal desktop width.
  • Details: No cause identified; no changes or settings mentioned; no steps tried are described.
  • Evidence: No screenshots or attachments.
  • Status: No solutions or guidance provided yet; issue remains unresolved.
Summarized with AI on January 11. AI used: gpt-5.
1

I am in the theme editor. I was editing in desktop view and for some reason, it started to display a very narrow view. I cannot make it go back.