No toggle. Transparency is done by shaders.
textures/mapname/transparentglass
{
qer_editorimage textures/mapname/transparentglasstexture.jpg
surfaceparm nolightmap
surfaceparm trans
surfaceparm solid
surfaceparm nomarks
{
map textures/mapname/transparentglasstexture.tga
tcGen environment
blendfunc GL_ONE GL_ONE
}
}