You can visualize dependencies as a graph with Guix out of the box [1]. While you can't easily setup "user dependencies" (except by editing the package definition) you can create profiles that install packages from a manifest file so you could have a profile with a manifest with xwayland and sway and then simply remove the profile if not needed. Guix already specifies runtime/dev dependencies.

[1]: https://guix.gnu.org/manual/en/html_node/Invoking-guix-graph...