Much like how you can hit the share button in any app to e.g. save a URL to Google Keep, I'd like to have this functionality for my Vikunja lists as well.
I figured, since the Vikunja frontend is just a webapp it might not be possible, but then I came across this webpage that seems to suggest this can be implemented in a fairly straightforward way.

Ideally users would be able to select what should be done with the received content (e.g. to which list to add, to add a 'Shared' tag, etc.), but by default adding it to a separate list called 'shared' so the items can be sorted by hand and moved to their intended location later on.