When I made my Customizer Expander (CE), I did a little deeper research on the "ConnectionGroup :local_22" which is responsible for main vertex groups of the body. There are 60 entries in "ConnectionGroup :local_22" and each of them is connected to a specific body scaling or rotation. I'll write all the "connections" here below before I forget.

clavicleL(1/2/3), clavicleR(4/5/6), 
shoulderR(7/8/9), shoulderL(10/11/12), 
elbowR(13/14/15), elbowL(16/17/18),
spine04(19/20/21), spine01(22/23/24),
spine02(25/26/27), spine03(28/29/30), 
buttR(31/32/33), buttL(34/35/36),
nil(37/38/39/40/41/42),
kneeL(43/44/45), hipR(46/47/48), 
hipL(49/50/51), kneeR(52/53/54), 
forearmR(55/56/57), forearmL(58/59/60)

Those number from 1 to 60 is ordinal numbers, and each body parts have three parameters each corresponding to (Y,X,Z) axis. For example, "Upper chest width" in CE is seen like below.

VertexDataF32 :spinec_vert_upchesty VertexDataF32.DataArray Array_F32 [ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0.9,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0];

As you look, only 20th entry has a content, and that points X-axis of spine04. In this case if you increase upper chest width slider, spine04 expands along the x-axis. One more example, bellybutton, that is the one of default slider, is coming up like:

VertexDataF32 :spinec_vert_button VertexDataF32.DataArray Array_F32 [ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0.5, 0, 0, -0.5, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0];

It's telling +0.5 on Y-axis of spine01, -0.5 on Y-axis of spine02, thats said if you increase this slider, spine01 will become longer and 02 become shorter at the same rate. If you've read this through, you already understand what CE is all about. By using application like WinMerge, you'll find instantly what was added in anim01.bs in CE.

Thanks for reading.