Steps to reproduce:
- Open https://www.mediawiki.org/wiki/Special:ExpandTemplates
- Insert {{:Accessibility guide for developers}} into Input text. (https://www.mediawiki.org/wiki/Accessibility_guide_for_developers is a long page with a TOC)
- Click on OK.
- A preview of the article inclusive the TOC is shown.
Current result: The TOC does not have a button to hide the TOC.
Expected result: The TOC should have a button to hide the TOC. This is occurs when the module mediawiki.toc is loaded.
The module mediawiki.toc is a less important module. But there may be more important module which should be loaded also an ExpandTemplate preview.