It is a little hard to arrange the icons position of applications on taskbar. The icon of application created earlier will be put in left than the later ones. Without 3rd party tools, you can not change the position unless you close the application and reopen it.
Wsizer is a tool which display the current window size and position, move/resize window by hotkeys, and as a bonus, it can also rearrange the position of the applicaitons.
1. Enable ‘Iconify window’ in the right menu
2. Press ‘alt’ and hold
3. Minimize the window you want to put on the rightest side
4. Find the icon of the window on ‘system tray’
5. click the cion to restore the window
Now, the window is the last one in taskbar.