* UserGuide - add sentence about graphic groups unification.

lib/doc/UserGuide.lyx

@@ -145,6 +145,7 @@ enumitem
 \html_math_output 0
 \html_css_as_file 0
 \html_be_strict true
+\author 5863208 "ab"
 \end_header
 
 \begin_body
@@ -19952,6 +19953,24 @@ LyX options
  tab.
  Joining an existing group can be done using the context menu of the image
  and checking the name of the desired group.
+
+\change_inserted 5863208 1518729806
+ If there are too many images which need to be assigned to a single group
+ you can simply put all of them into single selection and choose 
+\family sans
+Unify
+\begin_inset space ~
+\end_inset
+
+Graphics
+\begin_inset space ~
+\end_inset
+
+Groups
+\family default
+ in context menu.
+\change_unchanged
+
 \end_layout
 
 \begin_layout Section