Advice on instruments, Soundfonts, etc

Following on from this thread about instruments and Soundfonts:
https://musescore.org/en/comment/1204410#comment-1204410
I would like to ask for advice on how to handle my particular use case.

In short, my problem is that in Musescore 4, the Muse Sounds instruments don't give me what I need.
But when I go back to using Soundfonts, I'm finding choosing an instrument in Musescore 4 is so painfully slow that it's close to unuseable.

Let me give the background to my use case first.
- I am using Musescore to arrange for five voice parts, no instruments.
- I want to export from Musescore to MP3s, once for each voice part, with that voice part picked out, and the other parts in the background. I send these MP3s to my singers for them to practice from, and as a click-track against which we record their voices.
- I don't want to use Choir Oos and Choir Ahs, because the sound of the notes aren't clear enough for my singers to pick out individual notes from.
- My practice has been to use clarinet for the part I want to pick out, and an electric piano (like Tine Piano) for the backing vocals
- So I have been exporting to MP3 five times, going through each instrument, changing it to clarinet, exporting, then changing it back to piano again.

This worked reasonably well for me in MS3, though it was a bit fiddly finding and selecting the clarinet part. And I couldn't change the instrument in the score, because then Musescore would transport the clarinet part and I wouldn't get the notes I wanted.

Problem Statement (with Musescore 4)
- I don't want to use Muse Choir sounds - as with Choir Oo and Ah, the notes aren't clearly enough delineated for my singers to practice to
- I have been working around by going back to Soundfonts. However this is horribly slow.
- From the mixer I choose the sound button for the instrument, and choose Soundfonts from the drop-down
- I then have to hover over the right-facing triangle next to the Soundfonts option for 5-10 seconds, while nothing happens (and the previous option on the dropdown is highlighted)
- Eventually the list of Soundfonts will appear, though if I click too soon on the triangle then it will instantly disappear and I have to start again
- Then I can scroll down and down the Soundfonts until I find [071] Clarinet
- Then I have to choose Bank 0
- Then finally I can choose the Clarinet instrument
Repeating this five times, changing each instrument to Clarinet and back to Piano is so slow and fiddly,
I tried to make a screen recording of this to attach. But when I did so (with the Windows Game Centre), the menu drop down lists didn't show on the screen recording, so the video wasn't much use.

My configuration is
Revision OS: Windows 10 Version 2009 or later,
Arch.: x86_64,
MuseScore Studio version (64-bit): 4.3.2-241630831,
revision: 22b46f2.
Laptop is an HP Intel i& with 32 GB of RAM and a 1 TB SSD.

I can see that what I am trying to do is not the primary use case that MS4 was designed for.
And I really like MuseScore in other ways, and want to support the product, and want to be on the latest version.
But this frequent task is so painful that I'm getting discouraged.

Am I doing something wrong?
Is there an easier way of achieving what I want to do?
(I'm aware of voice synthesizers like EmVoice, but there's a lot of work needed to add get it to say the words, and I don't really need that, I just need a click track with a part clearly picked out against quieter backing instruments.)

Thanks for any advice you can offer.