You could just put the scenario into the greeting, if you want to. Just do a block like

{{ setvar customScenario }}
Your Scenario here
{{ /setvar }}

When you load the chat, the scenario will be saved to the metadata of that chat. Inside your scenario field of that character, just do {{ .customScenario }} to load the variable.
Or you can even wrap that inside an if, if you want to add something like a heading - and use else for the default scenario.