Highlighted corner OR folder icon
When you see a highlighted corner on a button, it means that when you select that button another board will load and come into view. This is how CoughDrop lets you access more than just the number of buttons that would reasonably fit on a single screen.
By default, CoughDrop will indicate buttons which open another speech board by highlighting the upper right corner of the button. However, if you would prefer to have a folder icon indicate that the button opens a new board you can make that change on your preferences page.
Open the drop-down menu under your username and select 'preferences.' In the 'general preferences' section check the box which reads 'show folder icons instead of colored corners for buttons that link to other boards.'