Hi. You can add another tab like this for example.
//get layers formLayout contents
string $LayersFormChildren[] = formLayout -q -ca $gLayerEditorForm;
// layers tabLayout
print ($LayersFormChildren[0] + "\n");
// create some UI to attach
string $attachTab = columnLayout -p $LayersFormChildren[0] newLayerTabCL;
button -l "My UI Button" -c "sphere" -p newLayerTabCL;
// add another tab to layers tabLayout
tabLayout -e -tl $attachTab "Added tab" -st $attachTab $LayersFormChildren[0];
Cheers.