Note: I haven't ever worked with C# before this, so this is basically trial and error, and lots of googling. If this isn't at the same sub-par level of coding standards as the main MS Paint IDE project, that's expected.
Paint Injector is a project for MS Paint IDE that adds buttons to the actual MS Paint program to interact with the IDE. It uses a fork of OpenTitlebarButtons, which is a library to add extra buttons to the title bar of windows.
Very early alpha screenshot of what this does currently (No modification to MS Paint):