Sharing dependencies between projects with PEP 582

[glatterf42]

Sorry if this is answered somewhere already, but I checked the docs and searched quickly here and couldn't find an answer.
We have several packages that belong together, but are not part of a monorepo setup: among others, ixmp, message_ix, and message-ix-models. So if they are installed from source, their repositories usually share a common parent directory, but not necessarily. Even though PEP 582 was unfortunately rejected, I would like to see how a setup using it would look like in our case. That is, I would like to have pdm manage one project with PEP 582, where any number of the packages above can be present as editable installs (that share the same dependency versions, then). What would be the best way to do this?

I imagine it's similar to managing a monorepo, but I'm not sure what to change specifically.