With Concepts for Windows 2021.10.2 and later, you can set different actions to your Surface Pen top button.
First, connect your Surface Pen via bluetooth. Go to Pen & Windows Ink settings and make sure the box "Allow apps to override the shortcut button behavior" is ticked.
Next, go to Concepts. Create a new drawing or open an existing one. Go to Settings. Scroll down to the "Stylus" section and set your preferred actions for Button Click, Button Double Click & Button Long Press.