You can signal interest and maybe draw someone else in now.
Pokemon Go has rolled out more changes to the raiding system.
An update today has added the ability to "RSVP" or schedule a time for participating in a raid battle. The signal includes an option to invite friends to participate.
This differs from a previous system of "EX Raids" in which a player would be invited at random to play a particularly challenging raid: this feature was depricated in 2020 as part of the game's pandemic adaptations.