Hit `/` in the composer, type the shortcut, send.
Saved replies (canned responses) live in Settings → Canned Responses. Each one has a shortcut like /welcome and a body.
In the composer, type / to open the picker, narrow with a few characters, press Enter.
The body can include placeholders that auto-fill from the conversation context:
{{first_name}} — contact's first name{{customer_code}} — internal code{{agent_name}} — replying agentVariables that have no value render as an empty string, so a half-set up reply never leaks raw {{ }}.