<li>\b Add button adds to the list a group of elements selected in the
viewer with pressed "Shift" key.</li>
<li><b>Select all</b> checkbox selects all groups.</li>
+<li><b>Show double elements IDs</b> checkbox shows/hides identifiers of
+elements in the 3D viewer.</li>
</ul></li>
<li><b>Edit selected group</b> list allows editing the selected group:
<br><br>
