Panadapters and slices are separate things. Panadapters can have up to 7MHz displayed bandwidth on a FLEX-6300. You may place one or two slices anywhere in the one or two panadapters displayed. There are no limits beyond this.
If you tune the panadapter where the slice no longer sits anywhere in the panadapter, we will mute the slice, but leave it for you so that when you return it is where you left it. You may also click the slice using the off-screen indicator in the panadapter and either quickly tune to it or close it if you want to do either of these things.