I just find it strangely hard to make a button to send constant value with Touch. It seems some people having same issue but there are still not very best solution…
Good compilation of other attempts to set a gadget to a default value.
rurik almost had it right In your example, change button1 to a Momentary button, then create a Panel Execute DAT that refers to button1, and put this 1-line script in the DAT:
click sliderhorzvalue/slider 0
or whatever default value you want. When you click the button, its panel value “select” goes 0 to 1, and the script runs.