Q Light Controller+

Is it possible to start a chaser with a GPIO high value but stop it when the value is low? I can trigger my chaser to start with the GPIO, but I want it to stop when I let go of the button, rather than having to have a stop button.

I guess you need to create a custom input profile and enable the "Generate an extra Press/Release when toggled" option
see http://www.qlcplus.org/docs/howto-input-profiles.html