Make Open-Shell Menu align to the working area instead of aligning to the taskbar

[AEAEAEAE4343]

Is your feature request related to a problem? Please describe.
A clear and concise description of what the problem is. Ex. I'm always frustrated when [...]
When using a custom taskbar replacement (as in a program that replaces explorer's taskbar completely) the start menu keeps it's alignment to explorer's taskbar even though the working area has changed to be bigger. See image:

Describe the solution you'd like
When the Start Menu displays it should align to the corner of the working area instead of just on top of the taskbar

Describe alternatives you've considered
I've tried changing the size of the taskbar but explorer refuses to change the taskbar size.

[AEAEAEAE4343]

I would love to make a PR to fix this issue, but I can't for the life of me figure out where I can find the code that decides the position of and displays the start menu. Can anyone give me a hint on that?