Thanks for the notification. Yes, we had a discussion whether it made sense with a local translation or an edit here, and ended up with just making the change locally. But we also believe the English label probably should be changed.
The Product Manager thinks that nobody (especially new people) will know what VisualEditor means.
That might very well be true. The question is rather, will they 1) understand source/visual any better, and 2) be more or less confused when hearing about wikitext and VisualEditor after first learning different terms?
Most new editors start in the mainspace, by editing an article. Do they see the name "VisualEditor" anywhere in that experience at the Swedish Wikipedia? (It's not mentioned at most wikis.)
Not directly, no (but the help text in the editor leads to w:sv:Wikipedia:VisualEditor/Användarguide). They see "Redigera" (Edit) and "Redigera wikitext" (Edit wikitext) (n.b. not "source"). And then the buttons to switch between editors while editing is "Visuell redigering" (Visual editing) and "Wikitextredigering" (Wikitext editing). So the most consistent text to use on the tabs would be these last two.
Yeah, it's kind of a mess. We might need you at https://phabricator.wikimedia.org/T256166 and related tasks. Some communities translate wikitext as wikicode, which helps a bit. (This kind of thing makes me wish for WordPerfect 5.2 on MS-DOS: I keep thinking about "Show codes".)