To Add a Trip Member, but not send a Trip Invite until a later point in time simply add the Trip Member details and "Un-Check" the send now box.
You can Send the Invite at a later point in time by clicking the Invites Tab, select the Trip Member and click Send Invite. Alternatively you can use the Send All Invites button to send to all.
Why use this?
We have added this because it is a common occurance that you will start receiving bookings for a trip well in advance of the Trip commencing. Whereas you may want to wait until, for example, 2 weeks to give your customers access to the trip in the SafeTravels mobile app.