When dragging items into the sequencer they will automatically be assigned to whichever server channel is currently the selected active channel. Double-click a different channel to activate it, and any items will then get that channel as their default channel when dragging to the sequencer.
If you aren't aware, you can also bulk change the server channel of several items in the sequencer by selecting them all and using the take inspector to change them all at once.
#XPression