Keeping a window visible on shared screen while switching workspaces on Ubuntu

I am using Ubuntu 24.04 LTS (X11) on my laptop, and suppose I want to use Deskreen to share a PDF viewer on my iPad while writing LaTeX on Ubuntu.

• I have two application windows open:
  1. A text editor for LaTeX writing.
  2. A PDF viewer to preview the compiled document.
• Both applications are in the same workspace, and the PDF viewer is visible on my iPad through Deskreen.
• However, when I switch to a different workspace, the shared PDF viewer on my iPad turns blank.

Workarounds I've Tried:

1. I attempted to create a virtual display using xrandr to extend my laptop screen on iPad, but I couldn't get it to work. The details are here: Use iPad as 2nd monitor of Ubuntu 24.04 LTS and also on GitHub.
2. As a temporary solution, I used Google Meet to share the PDF viewer separately. It works, but the process is not very automated and takes time to set up each time.

Question:

• How can I keep a specific window or workspace visible on iPad via Deskreen (or any better alternative tool) irrespective of workspace changes?