Right now, currently, you have to click on a button to enable the toolbar in Paint.net aka Paint dot net. Well, older versions of this program still support the toolbar, and still have most of the same features as the newer versions. So why keep updating Paint.net every week?.
As you can see in the above image, the toolbar is there, and that’s the way I like it, I seriously hate clicking on a stupid button to open up the toolbar. Sure, at least the color toolbar shows up but I don’t care about that. So, the link you must follow in order to download the older version of Paint.net aka Paint dot net, is here.
Hope that helps you in getting back your toolbar. Paint.net is a powerful program and so basic that I wish it was available on all platforms and didn’t require being updated all the time. That’s my dream. According to Wikipedia, Paint.net is no longer open source. That is the sad thing. I guess at least it’s still available for free.