Scripting BetterTouchTool using AppleScript
BetterTouchTool has a small but powerful AppleScript interface which will be described here.
The most current documentation for all supported AppleScript calls can directly be accessed via Apple's Script Editor app on macOS. Go to File => Open Dictionary => BetterTouchTool to access it there.
Note: There are some built-in variables, which can also be quite helpful:
Security
In general every application that is allowed to execute AppleScript could trigger these scripting functions. If you do not want this, you can define a shared secret which then must be included in all calls as "shared_secret" parameter.
The shared secret can be defined in the advanced preferences

Available Scripting Interfaces
trigger_named
This method will trigger the specified named trigger (which can be configured in the "Other" tab in BetterTouchTool.)
Standard AppleScript Example:
tell application "BetterTouchTool"
trigger_named "TriggerName"
end tell
JavaScript for Automation Example:
var BetterTouchTool = Application('BetterTouchTool');
BetterTouchTool.trigger_named("TriggerName");