In order to select many test persons, it is best to create a pseudo session (e.g. on 31.12.2023, 23:00) and invite the participants via this session.
If you only want to invite specific participants, go to the participants overview and select the participants you want to contact.
Then you can click on the field “execute” above the table and choose “send mass mails”.
Copy the invitation text into the free fields and all selected participants will receive the invitation for your experiment after sending the message.