Layout Option

If I Make change to Full score And hit apply then When I Select “P1” it Not affected

Please, See image below

Select the layout in the right panel before you start making changes.

I already make a change for each part, Now haw can I make all the same ?

How can I reset all the modified ?

Use the buttons in the bottom left corner. There’s a Reset button, and there’s also a Save As Default button. Alternatively select all three layouts in the right panel and then make the changes to all of them at once.