@timzafir it’s definitely working (at least in chrome, but since backend, it should work on any browser because backend does not depend on the browser).
Look over this workflow carefully: Nrb-tester | Bubble Editor
Here’s a video of me walking through this workflow (note that I significantly changed it to make the flow of things more apparent): https://drive.google.com/file/d/1iKOfYUs_Ed_8BsevXrjETcgOS-uq3cWp/view?usp=sharing
Basically, the merging takes some time (5 seconds for small PDFs) to complete… you may have an issue with the “Make changes to User…” step in your workflow, but the actual merging is definitely happening. You can also check your file manager to verify that the merged file completes (unless you disable that in the “Backend Merge…” step).