Unable to open VST and MIDI instrument panel In D4.3

I am unable to open the VST and MIDI instrument panel in Play mode in Dorico 4.3. This is happening with any and all files opened in my older MB Pro and also my M1 Mac mini. It is probably something really silly that I am missing but I haven’t been able to get it sorted and welcome any suggestions.

Can you attach a screenshot showing what you’re seeing in Play mode? I assume you can see the Track Inspector panel in Play mode? What happens when you click VST and MIDI next to the Track Inspector button?

Here it is. Using command-9 doesn’t open it (but works fine in the modes other than Play) and there is no arrow “button” to click.

EDIT: Last night I tried closing and reopening Dorico and also restarting both computers but this had no effect.

What do you expect to be seeing here? The VST plug-ins that used to be on the right side are now on the left in Dorico 4.3 (and showing in your image).

Perhaps I have misunderstood your inquiry.

It looks the same on my Windows machine:

Thank you! Yes, I haven’t been doing much with Dorico for awhile and forgot how this changed with version 4. I did say it was probably something silly and I guess I was right about that!