Yes, It's not possible to start a workflow from a tray.
I did manage to index an imported document using "Document Processing" https://help.docuware.com/#/home/63710/2/2
We are building a Workflow who could take a document from a tray, preserving the intelligent indexing data, and store the document within the workflow process.
The document is clean and simple, Intelligent Indexing is 100% efficient every time.
Main focus is to build a full-auto workflow without the need of human intervention (store dialog)
And the Source of the document is email attachment, so cannot use anchor from "Document Processing"
Thank you !