No. Existing participants aren't notified when you add new session times to a live study.

You can message participants to tell them about the new times, and they can then go back to your study and update their availability. In practice this is slow: it's extra effort for the participant, and extra back-and-forth for you.

Invite more participants than you need directly to the new times. Whoever is free accepts and confirms; anyone who isn't simply declines or ignores the invite. This is almost always faster than waiting for existing participants to update their availability.

For example, if you add one new session, invite around 5 suitable applicants to it rather than relying on a single person. Participants who accept after the slot is filled are told they're waitlisted as a backup. See Waitlisting participants.

To see who suits which times, see Where can I see participants' availabilities?