Screenshot: Narrow window
When space is scarce (for example at high zoom, or when the window is very narrow), the "View history" tab is moved to the drop-down menu (that also includes "Delete", "Move", etc.) so that the action remains accessible.
The "Edit" and "Edit source" tabs don't seem to do the same; they stay where they are, which prevents them from being used in similar situations (see attached screenshots).
It would imho make sense to migrate both tabs to the drop-down menu as well when there isn't enough space to display them at their usual location, so that users can still access the edit modes.