You can still create the Tx outside of the system with access to KMS. Set the “to”, “data”, and “value” items to do whatever you need and set the “from” address to the one that maps to the key pair that’s managed in KMS. All other values will be set in the system that’s connected to KMS if that makes sense. Before doing this you’ll need to do some test runs with manual transactions to find the right address that belongs to your key pair.