Change instruments without changing VST?

I need to change several instruments held by players - but only the “subtype”, e.g. different transpositions of the same brass instruments.

Is it possible to do this without changing the contents of the VSTs?

Currently, the ‘old slots’ stay as they are, and ‘new slots’ get added to the bottom of the list.

I’ve tried turning off the audio activation, then making the change, then turning it back on; but that doesn’t work.

I could re-apply the template, but I’ve made several manual adjustments.

No, it’s not possible. Dorico will always load a new sound for a changed instrument.