In the Select Instrument dialog, add an option to playback a single note of each instrument when it's clicked on
I tend to choose my instruments by timbre much more than by name, as I work mostly with electronic music and use Musescore as a rough draft or clarification of something I'm going to put into a DAW. I often have no idea what MIDI instrument would be closest to the sound I'm using in the DAW, so I have to spend a while trying out different instruments to see which one approximates it the best.
If there was an option, either in preferences (or better yet, in the select instruments dialog itself) to play a note from each instrument when it was clicked on, it would make things a lot easier. I wouldn't have to keep opening and closing it over and over to see what each instrument sounded like.
Oh also, if does end up being added and the option is within the dialog vs. being a preference in the options, it should stay ticked/unticked if you close and reopen the box. I imagine most people would have one setting they preferred, and wouldn't want to have to change it every time.
Comments
Instruments in the add instruments dialog do not actually have sounds assigned to them. They have banks in soundfonts assigned to them.
Here is the problem with your suggestion:
I have a custom instruments.xml file that is mapped to a special soundfont as my primary soundfont. It is not 100% GM standard so there are some sounds missing and some sounds added. If I select an instrument without a sound in my special soundfont it will always sound the grand piano (which is the first sound in the soundfont).
The problem is that instruments and sounds may be intermixed. You will also miss sounds in the soundfont. There is no instrument the defaults to muted trumpet sound (among several others) for example. You may want to use this sound but you will never hear it by simply adding an instrument.