A variable is a named value every flow can read as {{ vars.<name> }}: a signature, a shop link, a default keyword, a webhook URL. Change it once, every flow picks it up on its next run.
Add one
Dataset › Variables › Add variable: a Name (letters, digits, _) and a Value. Turn on Secret to hide the value after saving; flows still read it.
Use it
{ "message": "{{ vars.greeting | default:\"Hello\" }} from {{ vars.shopName }}" }
Variables are copied into what the run gets when it starts (variable), so a change applies to the next run, not one already going.
FAQ
What happens to flows when I delete a variable?
They get an empty value. Use | default:"…" where it matters.
Can a flow change a variable?
No. Variables are read-only in runs. Store changing values in a .