Hi @T8m, welcome to the forum! 
The short answer is yes, it is possible. The longer answer is it depends what autopilot firmware you’re running, and what kind of control you’re trying to achieve.
The main ideas are described in the documentation. We don’t yet have examples/walkthroughs of this functionality in the docs, but these two forum posts cover the relevant setup steps for integrations between Cockpit’s custom Actions, Data Lake, and Input Widgets 
If you happen to be using the Blue Robotics gripper then ArduSub has built in min/max momentary joystick button functions. If you specifically want on-screen control (or you’re not using ArduSub) then there are three relevant PWM ranges (for Opening/Stopped/Closing), which you’ll want to cover with either
- Three custom
MAV_CMD_DO_SET_SERVOActions, assigned to on-screen button widgets, or - A single Action, using a variable controlled by a slider
Feel free to follow up if you struggle with implementing something in particular