Think of adding a shader preset a bit like painting the surface section you selected. You can paint over it with a different paint but unless you hit undo you can’t “unpaint” it. You can also select a surface in the surface tab and copy it to apply to other surfaces. Handy if you made changes to one and want to copy it over to another
One great addition to studio 4 was being able to group select several similar surfaces. You can select ALL the surfaces that “match” and you have several choices how to do it. So lets say that you used a shader preset on several locations on an object and decid you want to change them. You use the surface select tool but you right click it. You get a list of choices of similar surfaces to select.