Fritzing is an open source graphical PCB development tool. What's unique about Fritzing is that it relies on vector graphic files so that it can render very beautiful diagrams at high resolutions. It's a very nice toolchain that takes your prototype from breadboard diagrams, all the way to Gerber production files.
In order to make a part, someone needs to "draw" it using a graphics design program. Then you can import the drawling into the parts editor and assign "pins" to the vector shapes. From the tutorials I've watched/read the most commonly used program for designing/editing SVG graphics for this purpose Inkscape.
I noticed on page 12 of 81 in the "UM1974 User manual STM32 Nucleo-144 boards" PDF there is a beautiful vector drawling of the Nucleo-144 Development board. I tried ripping it out of the datasheet by opening the PDF inside of Inkscape but it's a simplified image (not vector).
Is there any way you (ST) would consider providing me with the Vector graphic of these boards? There must be a file somewhere that created that image - can you send it to me? If so, I'll make the part in Fritzing and contribute it to the community.