@bernhard.boehm - This is a great feature request, there is still no way to parametrize the currency symbol in the formatting pane.
However, I don’t think you have to have duplicate dashboards. The workaround may still not be “elegant” and will increase your maintenance effort (I know from experience, this can be a pain to manage).
If you use Free-form layout and Visual Rules you can layer copies of the visual and use a parameter to show/hide the N versions you have with the different currency symbols.
This post is a good primer on how to use the show/hide Hide visual based on filters - #4 by robdhondt