The MS Basic choice in MS4 does not open a menu to choose a specific instrument

I am trying to use MS 4.0.2. When I open the program and assign some of the instruments to a particular sound via the Mixer menu (F10), I may not find the sound I want in the MuseSounds choice. Instead, I may have to assign an MS Basic sound to the instrument. The problem is, if I try to do that, no menu opens in the Mixer to let me choose which MS Basic sound I want to use.

For example, I want to use the instrument named "Warm Synth" on one of my tracks. There is no Warm Synth or Electronic soundfonts in Musesounds, so I have to choose the MS Basic soundfont. When I try to explore MS Basic and choose "Warm Pad Expr" as I used to do in MS 3.6, there is no such menu. In fact, no menu opens at all when I click on the MS Basic tab in the Mixer menu. I have no means to select a voice for my track. The only way I have found is to right-click on the name of the track in the sheet music, choose "Staff/Part Properties" then "Change Instrument". Only then does a menu open that will enable me to change/explore the sound of the synth in that track. Further, there is no "Warm Pad" sound in MS Basic.

Please enable the option to open the sound menu when MS Basic is chosen in the Mixer menu. Thanks.