Thanks Fred for the quick response, I've done the following and able to get the data
Added this snippet to the head of the page on which the bot is located
<script type="text/javascript" charset="utf-8">
Genesys("command", "Database.set", { messaging: { customAttributes: { token1: "this is from the web page" }}});
</script>
Thru a Messenger Deployment configured an Inbound Message initial flow to include a "Get Participant Data" action to pass on the Attribute "token1" to a variable called "Flow.token1" which is available in the Inbound Message Flow.
After the "Get Participant Data" I'm calling a "Call Bot Flow" action and passing the "Flow.token1" value to an Input variable in the Bot Flow called "Flow.token"
In one of the Intents within the Bot Flow, I'm displaying the value of "Flow.token" in a "Communication" action.