If the switch can also be "switched over" as a push-button (switching state only when pressed on), you can even use the dimming function by setting an additional function for the long push-button action. However, the dimming would then only go brighter or darker, then you would have to switch off again to start at the initial value. Most switches can only switch on and off, so you have to set the Shelly so that a toggle switch is connected and the Shelly switches the dimmer on when the input is on and switches the dimmer off again when the input is off. Ideally, you have a double push-button for the dimmer, then both inputs can be used with a short press to switch on/off and with a long press the brightness changes.

The Shelly can be mounted in a switch, but I don't think the dimming function will work, as your LED bar seems to have an internal dimmer setting that may not support an external setting!