[BUG] Unclear documentation for prop attribute in layout

[mstranne]

DESCRIPTION

Describe the bug It is not entirely clear how prop EX is to be used, an explanation of what exactly EX should contain would be good.

Desktop (please complete the following information):

• OS: [e.g. x64]
• Version [e.g. v1.1.4.2203]

Additional context Add any other context about the problem here.

(Do not write below this line)

---

DEVS' SECTION

ANALYSIS

Straightforward. Update documentation.

IMPLEMENTATION STEPS

(see also our Wiki for implementation guidelines)

• Implement the necessary changes in a new branch created here on GitHub
• Test your implementation

DOCUMENTATION STEPS

(see also our Wiki for further information)

• Update the changes log
• Add comments to your implementation
• Add Doxygen documentation comments
• Create or update the documentation articles (*.NHLP and *.NDB files, if needed)
• Update the language strings (*.NLNG files, if needed)

PULL REQUEST

• Create a pull request for your changes
• Fill out the template
• Assign @numere-org/maintainers as reviewers