i think you can use a function there.
Click the game layout screen on construct and under the section general select "function"
Then add an event function > on function, and name it whatever you want. Inside this event put the code to spawn all the buttons that you want to be spawned at once.
Then whenever you want to spawn all the buttons instead of writing the same code over and over again you just create the action function > call function and set the name of the function you'd like to use.
Hope it helps