Hi @christian.r.r, welcome to the forum.
You can put whatever data you want into the EditableList widget, so in principle yes.
Is the idea the user can select from that list instead of using the normal method of selecting a config node within a node's edit dialog with the select box?
If so, you may run into some issues because the editor does quite a lot of work under the covers when it knows about a relationship between a node and a config node. For example, it keeps track of a config node's users so it knows when a config node is unused.
There may also be issues around import/export - if the editor doesn't know about the relationship properly, then when a user exports your node, it won't know to bring the config node with it.
Allowing more custom relationships between nodes is something that's been hovering around for a while. I recently started work on a design in this area - https://github.com/node-red/designs/pull/37.
If you can describe what you're trying to do a bit more, it would be helpful to understand. There may be a simple solution/workaround for it today, and it may feed into the design.