If Anything in the left is highlighted, you will Never see a way to select an Other Instrument for optimization.
The Only way to select an instrument that Is Not in your default list...Or somewhere in one of the sub categories...is to have the cursor set to 'On The Fly'.
Then you have to look and make your selection within the Parameter window???
Which is way on the other side of the screen.
Please consider:
Put All Instrument selections in the same location.
Change 'On The Fly' to something like Select Another Instrument(s)
OR
Have the 'Instrument(s)' option in the Parameter Window appear All The Time...
Not just when 'On The Fly' is selected, because it does not appear if anything
is highlighted.

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