Not sure why you would have asked about rebooting in that case, since you should not be doing that at all under power. If you are mucking about under power, then that might explain why you think
There is really nothing you can do as far as moving or replacing disks while powered up. Even if you have hot-swappable hardware.
If you unplug a disk with the array started, for example, it will likely get disabled and have to be rebuilt, even if you don't actually break anything.
And there is no point in trying to replace a disk under power either, since Unraid won't do anything with the new disk until you assign it, which can't be done with the array started. It will just disable the disk you removed.
So,