Horrible

The microphone for voice to text input was placed there with the OneUI7.0 (or 6.1?) update.  Why they saw fit to remove it from it's position on the keyboard options bar is beyond me.  However, if you want it moveable *and* back on the keyboard (where it belongs), switch your keyboard to G-Board.  You are also right, it does not make sense that you can't reposition things on the navigation bar.  For a variety of reasons, people should be able to position the controls where it makes the most sense for them.  The best you can do is go to settings/general/keyboard and toggle on "show input method button on navigation bar" and then select which side of the bar you want it on.  I was under the impression that there was some way to add the microphone to the space bar on the Samsung keyboard, but I don't know as I don't use the Samsung keyboard.  But, I have seen random postings about it when they first made the change.  You might have to do a forum search for it, unless someone chimes in.