Using Gremlin, I can create a vertex in an Azure Cosmos DB graph by issuing
g.addV(\'the-label\').property(\'id\', \'the-id\')
and subsequently
Please look at this.
http://tinkerpop.apache.org/docs/current/reference/#coalesce-step
You can try
g.Inject(0).coalesce(__.V().has('id', 'the-id'), addV('the-label').property('id', 'the-id'))
btw, you won't able to find the vertex using g.V('the-label').has('id', 'the-id').
g.V() accepts vertex id as parameters and not vertex labels.