It all depends on how developed the 6th finger is. If it is an underdeveloped process, it is, of course, impossible to move it.
If it is a fully formed finger, it will bend and unbend like the rest. Its full functionality also depends on which finger it duplicates and how often a person uses fine motor skills of his hands. For example, the little finger is in conjunction with the ring finger. Try to make the little finger bend separately and leave the ring finger completely straight. Not working?
And finally, an amateur video from YouTube (not mine), where the boy has 6 fingers on his hands: https://youtu.be/MqBUSKT7-4A
Usually the sixth toe is removed in deep childhood (a child under one year old somewhere).
I had a sixth toe and it was removed just in childhood.
There is a scar and a slight bulge (the foot is deformed). Parents said until 14 that I cut myself, but from the age of 10 I began to doubt and suspect that the matter was unclean.
I suppose that if a finger remained, it could function calmly (at the site of the scar, of course there are nerve endings and I feel everything).
Depends on the degree of development of this very finger. The acquaintance, whom the sixth was removed in deep childhood, still feels it as an integral part of herself, and in the first years experienced some difficulties in capturing things, hoping for the support of the removed part
I will answer with my own example - as an independent finger is not recognized, does not move on its own - only together with the little finger, and does not even bend