How to delete "effect assignment " ?

In the same way how you assigned them. Just press and hold the fx slot softknob and stomp on the remote switch again.

from our precious Reference Manual:

Assigning switching functions to the Effect Buttons is simple: just press and hold an Effect Button and press the desired Module button, e.g. Module A, on the Profiler's front panel at the same time. Done! It also works the other way around: press and hold the Module Button on the Profiler first, then step on the desired Effect Button afterwards. The upper left LED of the Effect Button should now reflect the category color of the effect you assigned. Now, you can activate or bypass the selected effect by stepping on the button on your Profiler Remote. To undo a current assignment, simply perform the same assignment procedure again. Gone!