Steps to replicate the issue (include links if applicable):

• Go to a page that has many sections, such that the table of content expands past the body view port (on most resolutions this may be seen here: https://test.wikipedia.org/w/index.php?title=BigDockedTOC&oldid=584288&useskin=vector-2022 OR https://en.wikipedia.beta.wmflabs.org/wiki/T352930?useskin=vector-2022)
• Assuming the TOC is on the sidebar, click HIDE next to it
• Open the TOC from the menu next to the article title
• Attempt to scroll down to see items towards the bottom of the TOC

What happens?:

• The page layout rearranges when the TOC is scrolled toward the bottom of the screen, closing the TOC and preventing you from ever getting to the bottom
• ADDITIONALLY, even if you reopen the TOC from the now-relocated section, the TOC extends past the viewport on the bottom of the screen, preventing you from ever being able to scroll down to the items lower on the TOC

What should have happened instead?:

• Not sure what the "best" fix is, but suggest that dynamic section scrolling happen in the TOC, such as how the sidebar will produce a vertical scroll bar when needed

Software version (skip for WMF-hosted wikis like Wikipedia):
WMF production

Other information (browser name/version, screenshots, etc.):
Originally reported on enwiki by Steue, see https://en.wikipedia.org/w/index.php?title=Wikipedia:Village_pump_(technical)&oldid=1188674279#Hidden_ToC_dis-appeares_on_it's_own_during_scrolling

QA steps

• QA this task
• QA T352851 and determine whether the fix here addresses that one.

QA Results - Beta