Managing VSTs with two scores

I need to copy selected bars of music between two scores. However, opening both scores in separate windows causes Dorico to become unusable because of instrument swapping. Here is why.

Each time I select something in the other score, Dorico offloads all instruments of the current score and reloads all the instruments of that second score. These are Vienna Instruments with Vel.XF (big). And then vice versa, Dorico gets into that offload/Load waltz as I click back into the first score to paste in the music. With 20 instruments being tossed around like that, each cross score operation can last 15 minutes – which is totally unworkable!!

Is there a way to tell Dorico to ignore the instruments (e.g. just remain in some kind of engrave mode only) while I do the copy and paste operations?

P.S.
To emulate this condition, I went to Play mode and in the Track Inspector, selected each instrument and forced it to “—”. Well again, as each instrument was being dropped, Dorico offloaded all the other ones and reloaded them all, minus that one. I wasted another half hour doing just that.

Mind you, it’s not like my PC is too small: 12th Gen Intel(R) Core™ i7-12700 at 2.10 GHz with 128GB RAM and Windows 11 Pro version 22H2.

I’d like to add that after a while of this, Dorico simply crashed with a warning: “A serious problem has occurred” regarding VSTAudioEngine5.exe and a crash dump.

These Preferences govern what Dorico does with playback when you have multiple projects open:

The second one needs to be set to either Ask or Never. That way when you load a second project you have the option of not activating playback.
Alternatively you can use the power button in the transport to activate or deactivate playback for whichever project.

With playback only active in one project, you should find copying and pasting between the two projects much quicker, as no loading or unloading of instruments should take place.

Excellent! Many Kudos! Tks - you made my day