How to add a cautionary key signature before "Coda"

Dear developers and users,

Is there a way to add a cautionary key signature before “Coda”?

The original piece is “Bauern-Polka” of Strauss as follows:

In my arrangement, I did it as follows:

I hid the text “To Coda” by typing a white space into the “Custom text” box.
I checked the “Hide option” to hide the text “Coda”, and typed “Trio” using a System-attached text.

However, I could not find an option for displaying a cautionary key signature before Trio (of course, Dorico recognises it as Coda.)
Could anyone give me a good strategy?

Thanks in advance.

No, there’s no good support for this at the moment. In general Dorico does not “know” that the bar before the coda will be followed by a completely different bar elsewhere in the piece rather than the coda itself, so it doesn’t know how to show things like cautionary key signatures, time signatures, etc. at that position. Addressing this is certainly in our plans for the future.

Thank you for your kind and detail answer!