Just wanted to mention that this would be a useful feature for me. Had previously been bitten by this: https://www.postgresql.org/message-id/flat/CAMjNa7c4pKLZe%2BZ0V49isKycnXQ6Y%3D3BO-4Gsj3QAwsd2r7Wrw%40mail.gmail.com
Ended up "solving" by putting a where clause on all my exclusion constraints I didn't want used for most queries (WHERE 1=1). That allowed me "disable" that index for all queries unless they explicitly have a 1=1 constant in the where clause.
