Any updates on this in July 2020?
It looks like a simple basic functionality that one should be able to draw shapes of precise shape and position it on the canvas -
through expression where needed, rather than challenging manual labor.
Probably through a Properties panel associated with an object (of course it remains as an object does not become pixels).
A simple task I started to create a YouTube Channel art requiring four rectangles of sizes
2560 x 1440
2560 x 423
1855 x 423
1546 x 423
all centred on the canvas of size 2560 x 1440 has become an incredibly formidable task.
I can use Object Align effect for centering, but it is a hit and miss game for rectangle size by dragging using mouse or using keyboard.
I cannot get to precise sizes as it always jumps to by 2/3 pixels on either side.
Paint.Net developers -- appreciate your fixing this for everyone with a high priority.
Given the extensive features and capabilities of Paint.net, such basic missing functionality looks rather intriguing.
Thanks Sri.