I select slews of presets and press delete all the time. (Then select un-do, so the bank order isn't fussed up.) Did it with all banks some weeks ago. No problem there, because it likes when you delete them.
However, moving a bunch of presets to a different place can be problematic. Better to copy and paste (if you have the room) to make sure your presets aren't borked...although:
- I think copying is more stable than moving
- borking in my experience involves only the amp block advanced parameters, and not all the presets moved will get borked, so if there's an un-borked preset that shares all amp block attributes with a borked preset, just copy and paste the block from one to the other. Or, even easier, if the adv-pams are stock, simply re-select the amp model in the menu.