[Jazzy Boomers]

If a MIDI USB connexion is set, removing the câble will lost configuration in Mobile Sheet 

In addition, you have to re-configure all Midi setting in all songs ?

[Zubersoft]

No, disconnecting a MIDI device will not cause any loss of settings you have applied to songs or anything of that sort.  You should be able to just plug it back in and the MIDI connection will be resumed.

Mike