It is actually quite simple to bundle multiple skins in a single skin. What you do is create a ‘master’ UIS file which contains code like that below. What it actually does is indicate how many skins are bundled, and then for each of them you need to specify the ‘sub design’ name and the file containing its UIS code. Each of these files is then just a UIS file as you have created previously.

[SkinStyles]
Number = 3

[SkinStyle0]
Name = XP Cobalt
Skin = XPCobalt.uis

[SkinStyle1]
Name = XP Cobalt Yellow
Skin = XPCobaltY.sss

[SkinStyle2]
Name = XP Cobalt Green
Skin = XPCobaltG.sss