A nice idea was added in a comment to the hackaday review:
I’d like to be able to design a sub-module (e.g. maybe an analogue filter, or maybe a MCU and its supporting hardware), create a PCB layout for it… then in another project, import that other project as a component with its own footprint.
Thus, inside the schematic for the “superproject”, instances of the “subproject” would appear as a “black box” components and in PCB layout, you’d just place “copies” of the subproject’s laid out PCB, before drawing wires and other connections between them and the rest of your circuit.
Not sure how designations would be handled, maybe they just get prefixed,or it could be they get mapped and re-numbered so they flow naturally in the parent schematic.
Doing this would save a lot of time. You could design your sub-circuits once, and literally re-use them like you do for components now.
Some kind of “shareable unit” would be great, either as a schematic and/or as a PCB layout.
I guess the cleanest way would be to merge the shared circuit into the target project.