Webflow is so flexible that you can this now without much effort or retrofit:
Create a wrapper for your page content:
- create a new section wrapper and place all of your page content elements and sections inside. Name the section class "content".
Create a tracing overlay / backdrop:
- drop a div onto the top of you stage and name the class "tracing".
- load your layout image as a background of the tracing with a the background image aligned top.
- set the div to 100% width and a height to match your layout jpg.
- set the tracing div to absolute (it will scroll aligned with the page, but should not affect the flow of other elements.)
- use z-index 100 to pop the tracing layer on top and adjust opacity to taste. (note that you cannot select any object you add to the page with the tracing on top unless the z-index is higher in the stack...
You can temporarily bump the content section on top by setting its position to relative which enables the z-index but remains in the flow. Set its z-index to 200. It works like a champ and it allows me to float everything on top by just toggling relative and auto for my section wrapper.
Adjust light and dark color or greys into your body temporarily to dim or create contrast with elements you are creating on top.
I just started playing with this when I read your post, but have been thinking about doing the same thing for a week. Looks super promising. I would be really interested to hear about your results. Would be awesome to have a solid technique for this until it is implemented in Webflow.
I was thinking you could even set a toggle on the live page that would allow you to show and hide the designers' original tracing layout layer for internal proofing and critical alignment. May be relatively simple to do with JS if it can't be done through a CSS interaction - off to try that next.
Be absolutely sure you clean up your classes and delete tracing from your final CSS when publishing the live site! That would be a huge loading hit to leave that giant unused background image in the CSS.
Thanks for nudging this to the top of my todo list - hope it works!