This was originally an idea by @lionel.kai that was archived. Let's not let the same fate happen twice!
I would like to see legends be listable in view schedules. In the case where a Legend is on multiple sheets (common), the Sheet Name and Sheet Number could just read <varies>. Or there could be another option in the Sorting/Grouping tab for "Itemize every Legend Instance". Then you could itemize every instance and see what sheets they are on or not. The Detail Number would be blank.
If you don't want to see legends in your view list, filter them out.
If that cannot work, creating a new schedule view type specifically for legends would work too. I'd prefer to see it incorporated into the existing view list though.