Is there a way to add items to the Queue without using a UiPath process? For example, could I have an external program or web app create a queue item and add it to an Orchestrator Queue so that a UiPath process can process it?
You can also you choose the programming language you want to use the API and the above link will give you some starter code. Then you can integrate it with your programming language of choice.
Another way to know more about the API endpoints you can using the inbuild swagger documentation in either cloud or on-premises orchestrator. You just have to add /swagger at the end of your Orchestrator instance.