Since the first version of Secrets if you hover over a service associated with a Login you can quickly connect to that service by clicking the button. For example, if you have
https://www.icloud.com associated with your Apple ID Login clicking that button will open that page on Safari.
This feature works out of the box for
https services using Safari or Chrome, and
telnet using Terminal. But if you have Transmit installed on your Mac, Secrets will prefer to use it for all service types it supports, includings services such as Amazon S3 and WebDav!
This site, for instance, is hosted on Amazon s3. I have a Login item in Secrets with the credentials for accessing the S3 bucket and an associated service with the URL
s3://s3.amazonaws.com/outercorner.com. Everytime I need to update the site, I can just click the button and it will open a Transmit window already connected to the bucket.
Go ahead, give it a try. This integration works with both Transmit 5 and Transmit 4.