I would like to know how to get a vertical file switcher on the left side i.e. in the left sidebar in Notepad++ 5.5?
I would like to have something like this as shown from the gedit editor?
You need to enable the 'Document Switcher' in the Peferences->General tab (it's a check box).
Once it's been enabled you should be able to just drag the window by the title bar onto the left side (it can be a bit fiddly for NP++ to detect the new location).