A related idea is that if this feature is implemented, it would be helpful to also have an option to resize the current Canvas view so that it includes all cards linked to the selected card. Perhaps this could function sort of like an implicit, dynamic definition of the selected card and all its connected cards as a temporary group, with a “zoom to selection” option for that implicit group.
Another related idea might be to have an option for this highlighting functionality to be available when hovering over a card rather than having to click to select it.