EDIT : That bar was solely for the Video Toolbox until they added Sidebar on MIUI 13.
(now the rest of this post has gone awry )
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'm currently using a Poco F2 which has a slightly different settings menu. I have a Mi 10 at home.
Can you swipe it open as below.
I remember now it was originally the Video Toolbox bar but expanded / changed with MIUI 13 in to an extra sidebar of apps similar to Quick Ball (?), depending if both are now selected in Sidebar.
Could it also be a curved line which is opens to become a Quick Ball which is similar?
Try both Additional Settings or Special Features and I'll check my Mi 10 later.
(Yeh the bar doesn't appear on my screenshots either)