In track mode, make sure the record button is pressed to save mute states (the big red one one next to the play button). Whilst the button is pressed and lit red, any changes you make - turning tracks on or off - will be saved when you switch to previously saved sequences or save the current mute states to a new sequence.
If you want to call up a sequence and mess around with the mute states without saving those changes back into the sequence (think of it as non destructive editing) make sure save mute states is off (record button unlit).
But remember, once you are happy with your new combination of mute states, hit record and then choose a new sequence slot to save it or switch to an existing sequence to overwrite the previous mute state for the sequence you are working in.
Turn it off again when you are performing or experimenting non destructively so you don’t lose your “default” mute state for that sequence.