Specify Service Layer Credits dynamic text by layer

[MattSmithCarto]

I would like to be able to specify which layer I'm displaying credit for.

If I'm creating an exported map and I want to have a section in marginalia talking about Imagery sources and using dynamic text to do so (i.e. Credits: <dyn type="mapFrame" name="Map Frame" property="credits"/>), I'd like to be able to specify the layer I'm crediting, so I'm not also crediting other map services that I might list in a different place. 

To summarise, I don't always want the service layer credits as one continuous string.

[JenniferBorlick]

That's a good idea. There are many "work arounds" I see for people hiding the service credits all together when the string is horribly long. This would help to prevent that. If you could put the individual pieces of it where you want, people will be less likely to completely hide it and ensure everyone gets credit.