Store variables can be used across various streams. The big difference compared to temporary and helmut variables are that those can be created, modified and deleted within a stream.
For further informations have a look here: Stream Variable Store
The wildcard is used in the following ways:
Variable key: test1
Variable value: hello
{store.variable.?}
For the following input (?) --> test1
{store.variable.test1}
The output is going to be --> hello
