From MFB support:

You need the step mode. Press and hold shift plus step 15, now press step15 until the red led flash. Then save with the select button. Now you are able to program each step with different parameters.

From user Skawa:


1) go to step mode rec + instrument.
2)then hold down select and hit the steps you want to plock. the steps selected will then blink letting you know their editable .
3)change your prams decay, tune, attack ect.. you will hear only the steps that are blinking change.
4) to lockem in hit select the step lights will stop blinking and save your changes
5) if you want more diffrent plock steps just repeat from number 2 ( ie hold select + hit the steps you want to edit.)

note: When you select the steps for edit ( ie select+steps) the only changes that will occur are what knobs you move. this allows you to change just the decay on say the b drum, with the rest of the sound in tack .