How do I add a response button in Gmail?
Select the Gmail account you want to address. Tap the check box on Smart Reply and / or Smart Compose to toggle the mode on. You can also enable (or disable) “Smart features and personalization” or “Smart features and personalization to other Google products.”
How do I type the symbol in Gmail?
You can also use a '+' symbol in place of the '@' symbol. The two work the same way. This means, when you compose a mail, in its body, you can now tag a person to whom something is specifically targeted at. To do so, all you have to do is make the @ symbol and start typing their name.