Our CTO has been lobbying for this feature for a while now. It's on our roadmap for a future version. Because Eluma is relatively new, and the collections people have created are also relatively new, we've partly assumed that the links in the Elumaverse are all new enough that the vast majority will not be dead. It would be a nice feature to help clean up any dead links you had in your old bookmark manager so that dead ones don't import.