Shift clicking and sorting by checkboxes

help.md

@@ -156,6 +156,8 @@ The table of instances in the center of the output page lists all 134 instances.
 
 ![Table of instances](/assets/image1.png)
 
+The table of instances has these interactivity features. Click on column headers to sort the table rows by the column; click again to reverse the ordering. Use the checkboxes to select instances; selected instances appear in the coordinate window.  After clicking one checkbox, shift clicking another checkbox selects all instances between the two, irrespective of the ordering of the rows.  Click on the header of the checkbox column to put the checked instances at the top of the table; click again to put them at the bottom.
+
 #### Coordinate window
 Below, we show the instances from 7M5D|1|2 (left) and from 5J7L|1|AA (right), together with their superposition (center).  One can use the checkboxes in the table to select which instances to display; when multiple instances are displayed, they are superimposed.  The coordinates can be rotated by clicking and dragging in the window.  One can turn on or off the display of nucleotide sequence and number.  Default coloring uses red for A, yellow for C, green for G, cyan for U, and CPK for modified nucleotides.  CPK coloring can be selected for all nucleotides.