Add voltage lack indicator inside coupling section

[cedrtheb]

• Do you want to request a feature or report a bug?

• What is the current behavior?

• If the current behavior is a bug, please provide the steps to reproduce and if possible a minimal demo of the problem

• What is the expected behavior?

• What is the motivation / use case for changing the behavior?

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  • PowSyBl Version: ...
  • OS Version: ...

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[flo-dup]

Would you like that indicator to be on the vertical or the horizontal part of the coupling section?