Why do we need 2 things in the menu bar?

[IanAtSalt]

It seems like the arrow button itself can be the delineator. Anything to the left of it will be hidden, anything to the right will not. Was very confusing to figure out what would be hidden after clicking the arrow until I moved the straight vertical bar around.

[UeharaYou]

Yes it's not intuitive, but this is the easiest way of implementation.

Just think this way: It allows you to move the ">" toggle further right, and still have some icons of its left always shown.

If still not convinced, you might try my fork with "|"s hidden by default.

[shinebayar-g]

+1. Right side of the < is always visible anyways, there is no secondary | needed. If | is placed right side of the > it's even more confusing (doesn't do anything).