• External web form - Task Id

    I find very poor that there is no way to use a form in the steps of a workflow and user has to fill the information in the decision area that give very limited possibility to show information , rich fields etc. but hopefully this is something that will come soon with a new version.
    In the while I would like to use external customer web page as a workaround, at least for some activity where the answer require full screen , list of values and a nice form to fill relying on the docuware workflow engine.

    My idea is to have a link in the decision area that call my page so the user open the external link , fill the form and via api I can interact with Docuware decision send data and even save document .
    What I need in my external link is the Instance ID of the workflow which I cannot see as an available System Field in the workflow designer, am I missing something ? 
    How can I know , without looping on all the active instances , what is the workflow and activity the user has to work on ?

    I can assign via api a unique custom GuiId to the workflow and I can use this as a key field for the workflow, but is there any way to query the workflow engine via api and filter based on the value of a variable to get the instance reference ?