Interesting use case Romain!

Unfortunately, there is currently no way to modify the Font in any way in Visual Overview dynamically. Feel free to make a feature suggestion though.

You could consider using a visually different solution for now; for instance with a regexreplace and param placeholder, coupled with the BackgroundColor shape data?

For example, assuming

• Element with name "E1"
• Parameter with ID 11
• Use case where the shape needs to be green when value is true and red when false

1. Color your shape green. This will be the default color and avoids you having to nest another regexreplace below.
2. In your shape, add shape data "BackgroundColor" and set its value to [regexreplace:false,[param:E1,11],Red]

The above will then color the shape green by default. The placeholder will resolve to "Red" when the value of the parameter matches your regex "false", thus making the background color red when the value is false.