Samsung
Add Members to a Contact Group auf Samsung
Samsung Contacts hides the option to add group members behind an extra edit step, which is why new contacts often stay outside a group even after being saved to the phone. The group screen only lists current members and gives no obvious hint for adding more.
To add a member, use Tap on Contacts ➤ Open the Menu ➤ Choose a Group ➤ Tap on Edit ➤ Tap on Add member ➤ Select the desired Contacts and tap Done ➤ Tap on Save. This path works the same whether you add one contact or several at once.
Group membership controls which contacts receive group messages and appear together when you start a group call. A contact left out of the group will not get those group messages, even if the number is stored correctly elsewhere on the phone.
If you only need to reach a few people once, a manual multi-recipient message is faster than editing the group. Use group editing when the same set of contacts needs to stay reachable together over time.