no LibreOffice icon in taskbar when directly opening a document file

Question

First, i don't think it's an duplicate of:
no LibreOffice icon in applications bar and/or LibreOffice icons missing from Unity task panel

I am using:

• Ubuntu [15.04] with Cinnamon[2.8.0]-Desktop
  
• LibreOffice [4.4.6.3]
  

(UPDATE, I upgraded my system to:)

• Ubuntu [15.10] with Cinnamon[2.8.6]-Desktop
  
• LibreOffice [5.0.2.2]
  

My problem:
When i double-click an *.doc or *.xls (or any other LO-) file (in Nemo[2.8.0] [2.8.6]),
LibreOffice opens and shows up the document, but with no TaskBar-Icon.

However, [ALT-TAB] works and shows up all open (LibreOffice-)Windows!

But:
When i start LibreOffice via *.desktop shortcut or
via command-line (e.g:libreoffice --calc) the LibreOffice-Icon is displayed/shown in the taskbar.

Answer 1

I had the same problem using kazam software to record but i couldn't find out what was the problem, so i came up with another solution...
I used the 'Hot Corners' to switch between windows...

1. From taskbar open the 'System Settings'
   
   
   

2. Now click on 'Hot Corners' to open the settings
   
   
   

3. In here choose one of the Corners and set the event to 'Show all windows' and set the 'Icon visible' and 'Hover enable' to checked.
   
   

   

Now When you take your cursor to the corner, you'll see all open windows and you can easily switch to each of them.

Example :