[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)

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DEVS' SECTION

ANALYSIS

(Describe, what's the issue and which changes have to be made)

IMPLEMENTATION STEPS

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

DOCUMENTATION STEPS

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• 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

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