The articles
https://vborg.vbsupport.ru/forumdisplay.php?f=184 are probably the best place to start though I'd say that they don't really tell you too much. I tend to find that experimenting and asking questions when stuck seem to work the best. The developer documentation is pretty much non existent lol (Well they were for 3.x they MAY have improved for 4.x but I've not really spent too long looking).
There's a few articles that will tell you how to create custom vb pages etc but I'll let someone else recommend the articles to look at as I'm still a beginner when it comes to creating mods lol. Something to keep in mind though is that a lot of things have changed in terms of plugin development for the new 4.x version. So keep in mind if you look at the 3.x articles that they'll require some changes to work on 4.x.