Currently in paint.net there is no way to adjust a line to keep it straight. Let me explain with a short use-case.
Let's say I want to draw a ladder, I've got some parts done, what's left is just one straight line:
Then, I add it:
But—I've overshot it—oh no!
So I zoom in to see exactly where I need to put it:
Aha! Fixed! But wait—
The line is not straight anymore!
What I expect to make is:
But currently, (let's say on wide (or any other) image files, where you cannot accurately place both start and end points) there is no possibility to adjust straight line start and end points.
If I'm not mistaken, this was supported a while (8-15 years) ago, but recently it's gone. It's so strange that there is currently no possibility to do this.
I don't know how it could work, but the simplest (personally intuitive) solution would have straight lines as an option in the line tool.
Another solution would be to hold a button (alt? shift? ctrl?) while dragging one of the two endpoints, but this would be hard to discover and hidden.
Maybe I'm missing something? Maybe there's currently a way to adjust straight lines, but I'm unaware of it?