t seems that Microsoft has finally responded! In Windows 10, within the Surface app, under the pen settings tab, THERE IS NOW PEN CUSTOMIZATION DROP DOWN LISTS FOR THE TOP ERASER BUTTON. Not only that, but the single click, double click & hold down actions can have separate actions customized! Each button action has a drop down list. Each drop down list is the same, with four choices 1) xxx (default), 2) Disable, 3) Launch a store app & 4) Launch a desktop app (UPDATE : Press and Hold has a 5th choice "Cortana Ink Reminder") If you choose 3) Launch a store app, then a list of the apps are provided automatically for you to choose in a drop down list that appears If you choose 4) Launch a desktop app, then a drop down list appears that is not populated with programs, but instead, a browse button that allows you to search for the file location that you want to launch. Although not robust in terms of detail, with only the ability to command "OPEN" a file, it nevertheless allows the opening up of OneNote desktop version as opposed to the mobile app version! Appreciate Microsoft embedding this functionality within Windows instead of using a third party scripting language! I do not know whether this is available only to the Surface Pro 4 pen (pictured) or also to the Surface 3 pen. Would be interested to find out! Merry Christmas!