When $wgDebugToolbar (doc) is set to true, and the Vector skin is being used, the button that toggles screen content view gets almost completely hidden (see image below).
Expected behavior
The toggle button should be able to somehow detect that the debug toolbar is enabled and somehow just float immediately on top of it.
The full screen toggle will be removed as part of T362148, however this area is also used by other extensions e.g. Growth uses it to add a help icon https://gerrit.wikimedia.org/g/mediawiki/extensions/GrowthExperiments/+/60eb364ddbc4cd8814f00ab246cd442c0b9dc177/modules/ext.growthExperiments.HelpPanel/HelpPanelCta.js#39
Special:Preferences is also affected since the sticky footer is there (cd150ad0f1ca925a0904fb24b6585a9f34655ff4)
As @Jdlrobson points out, this toggle button was removed as part of T362148, so I'm marking this task as resolved. If I'm mistaken or the other use-cases are still an issue, feel free to re-open this task.