Hi Mohammad Ali Qureshi,
If you close the Assignable display properly after making the desired settings (using the "Exit" button or touching the "X" symbol), these settings are automatically saved in the so-called "System Setup" and are also available after restarting the keyboard.
However, if you do not close the Assignable display as mentioned (but leave it open in the background), the settings you have made will not be saved. In principle, this applies to all setting displays that do not have an explicit "Save" function.
Since the Assignable settings can also be saved in Registrations (separate check boxes for "Foot Pedals" and "Assignable Buttons"), these settings can also be changed by calling up Registrations in which the relevant parameter group was saved.
In order to be able to quickly return to certain assignable settings, it is recommended (as already mentioned by Fred) to create at least one so-called "Setup Registration" which contains the personally preferred settings.
By the way, in order to prevent Registrations from calling up certain settings, the FREEZE function can be used: Press "Direct Access > Freeze", check the desired boxes, press "Exit" and then switch on "Freeze" (button lights up).
Hope this helps!
Best regards,
Chris