You can add other attendees of the event to a meeting. The meeting becomes a group meeting with one shared chat and one video room. There is no shareable room link, and you can't invite people who are not attending the event.
Where to find it
In an existing meeting: open the meeting chat, open the ⋯ menu at the top right and select Invite others.
When suggesting a new meeting: select Add others at the bottom of the Suggest meeting screen. See Group meetings.
The path is the same in the mobile app and the web app.
Invite attendees to an existing meeting
Open the meeting chat and select ⋯ > Invite others.
Read Creating a group meeting. It says that inviting other attendees converts the meeting to a group meeting, that invitees only see messages sent after they join, and that this can't be undone. Select Continue. Check Don't show this message again to skip this screen for this event.
On Invite others, choose attendees from Matches, Bookmarked or All networking. Use Search to find a person. The lists only show attendees who are free at the meeting's time. Select Continue.
Edit Your message. The app prefills "Hi, I am having a meeting with <name>. You might be interested in this one."
Select Send invite.
The app shows "Invite sent". Each invited attendee gets a push notification "Group meeting request from <your name>" and an email "<your name> invited you to a group meeting". They answer Going? with Yes or No. The chat shows "<your name> invited" with the people you added. Inviting others does not use your meeting request quota.
Good to know
Invite others only appears when the organizer has turned on group meetings and the meeting's networking slot is in an area that allows them. Meetings without a time slot can't become group meetings. If you don't see Invite others, the organizer has turned it off.
You can invite others to accepted and pending meetings, but not before the other person has joined the app.
After the meeting becomes a group meeting, only the two original participants (you and the person you first met with) can invite more people, from ⋯ > View attending > Invite others.
The organizer sets the group size limit, between 2 and 100 people in total. The app lets you pick up to 15 people in total and then shows You have reached the maximum number of allowed invites. If the organizer's limit is lower, sending fails with "Maximum of <n> participants allowed".
Invited people only see chat messages sent after they were invited.
A meeting labeled Arranged by organizer (or the name your organizer gave it) can be locked. Then Invite others is hidden.
Troubleshooting
This networking area is for one-to-one meetings only
Add others is disabled because the chosen time slot is in a networking area for 1:1 meetings. Select Change and pick a slot in another area.
Add at least one attendee to suggest a group meeting
The chosen slot is in an area for group meetings only. Add at least one attendee with Add others before you select Send request.