At the moment, "Display value" form fields are the only field type where one cannot define/overwrite a form field ID, which makes it impossible to access the display value field by ID in the DOM of a form.
Steps to reproduce
1. Via App Designer create a simple process: start event->user task->end event
2. In start event add a form with a text field "mytext"
3. In the user task add a form with a display value field and display the value of field "mytext"
NOTE: You cannot define a field ID for the display value field
4. Create a process app with the designed process, publish it and lauch the process
5. In the start form, fill in some value for "mytext"
6. Using HTML inspector in browser tools, inspect the display value form field´s HTML code
The display value field does not provide an ID and is not accessible in the forms DOM.
As all other form fields have IDs by default and the ID can be defined/overwritten, also the display value field should have an ID.
"We use the JSON object of the form and parse it. For that we require the id of the fields. As a user, we should know what is the ID of the field so that i can use its value in script task or any other place."
Reproduced current state in APS 1.6.2