As everyone knows that cards that are on the so-called "Reserved List" are highly desirable for collectors as well as investors, it would be need to have a filter option for these specific cards. A complete list of all cards that have been put on the "Reserved List" can be found here:
https://mtg.fandom.com/wiki/Reserved_List

You might not be surprised to learn that this has been requested many times! I also want this filter.

The closest we've got is creating a Reserved List "deck", which can help out in some cases. You don't need to create one from scratch -- just copy psrex's deck (under Tools > Copy / Duplicate).