Hi, as far as I am aware, there is no specific capability to reposition the fermata. You could, however, drag the fermata to the intended location and hope that with a little adjustment, it will be fixed. The issue with this method is that repositioning rests and navigation markings affects the spacing of the staves. It might be possible to increase the space between staves, allowing repositioning to take place, but I have not tried this. I have, however, placed the fermata at the bottom of the stave on my own composition, using the method described, without much difficulty.
Failing that, I would suggest it as a Feature Request. Good luck.