Hello whbemmel_4785!
I'm not sure if I understand your question.
If you want to trigger Dimension Strings I, add [VSL Dimension Strings I] instruments in Sibelius and the "Dimension..." programs on the Manual Sound Sets page.
If you want to trigger Dimension Strings II, add [VSL Dimension Strings II] instruments in Sibelius and the "Dimension... II" programs on the Manual Sound Sets page.
If you want to trigger them both and switch between senza sordino and con sordino, you can do as described in the Sibelius Integration manual.
https://www.vsl.co.at/tutorials/guides/sibelius-integration/general-optimization#con-sordino
Best regards,
Andi
Vienna Symphonic Library