This is absolutely do-able in Webflow without the plugin, with just a little bit of custom code:
Insert a div, give it a class e.g. sections-wrapper and nest all of your cd-section elements inside of it
Insert a HTML Embed element inside of the sections-wrapper and paste the following code:
- Set the position of cd-section to relative and set the top position to 0px
- Finally, give each cd-section a combo class (1, 2, 3, 4, 5 etc.) and give each consecutive section a higher z-index than the previous i.e.the first section could be z-index 1, next section z-index 2 etc.
And that should be you set! If everything works, each time a section reaches the top of the viewport it should stick as the next section (with a higher z-index) continues to scroll up overlapping it.
Let me know how you get on.