There's a support-form realized with express form.
How can I prepopulate a field "referring product" with an attribute of the current page?
I'm looking for a way in my custom view.php of the express-form.
Maybe look specifically at the part to modify the "required" text as it's probably the same steps as what you'd have to do.
Otherwise, there might be a better solution. Easier in any case. If you want that field to be automatically filled I suppose you don't want the user to mess with it or modify it. If that's the case I suggest you have a look at my package Express Hidden Data
It adds several hidden attributes types to your form. The one that would work for you is the dynamic data one because it is extendable. Look at the bottom of the page there's a link to a GitHub repo with an example, it's really easy.
So basically you can have it grab the page attribute, output the value to a hidden field and it's submitted along witht he form. No user input and no user interference.
If you think it could solve your problem and have any questions, feel free to post here or ping me by Private Message.
One problem is the output in the email:
In reports / submitted forms you can read the pagename and username and timestamp.
In the email there's only the collection-ID, user-ID and a timestamp-hash.
Could you output this in a readable format?
It's pretty easy to change but it will make your email an HTML email instead of a plain text email and will show the data exactly as in the report with links and all.
If you can live with that I'll send you a modified email template and will show you how to use it.
Update to version 1.0.3 and you should be good to go.
And if you like the package and it saves you time and effort I'd really appreciate it if you could leave a review (https://www.concrete5.org/marketplace/addons/hidden-data-attributes-for-express/reviews).
No pressure whatsoever of course ;-)