Can't reassemble Shimano bar-end shifters
You have probably resolved your problem, but others may encounter it; I did.
Number the 6 parts in your photographs from left to right so they correspond to the exploded sketch: 8--the nut; 7 and 7a (7 is the mount that enters the bar; 7a is the notched, cylindrical disk that is a separate piece from the mount.);  6--the single tabbed notched washer; 5--the double tabbed washer; 4--the lever; and 321-- the pronged ratchet mech, conical plastic cover, and bolt.
Washer 5 rests with the tabs against either end of the raised segment of 4 (lower photo).  Insert 321 into the back side of 4.  Place 6 on top of 5 with the tab up and notches aligned with the prongs of 321.  Place 7a on top.  The tab shown at the top of 7 in the sketch fits between the single tab and the raised segment.  All the parts are “fiddly” but will fit together only one way; if any parts are canted even slightly, try again.
I found it helpful to put a dot of nail polish on 321 and 7a in way of the single tab of 6.
Install the parts on the mount, tighten the bolt, and check the function.