Exploring the Input system myself so figured I’d take a crack at this! You need to make use of the Combo trigger.
(1) Create N + 1 input actions, where N is the number of buttons that need to be pressed. For example, I created IA_ComboLeft and IA_ComboRight for my two buttons, and IA_Combo to represent the ‘combination’ of both. These don’t need any special properties, they can all be standard input actions like any other button.
(2) In your Input Mapping Context, add your individual combo buttons (ComboLeft and ComboRight) like normal, and specify a key for each.
(3) Add your third Combo (representing both at the same time or quickly following each other) input action to the IMC, then drill down in the properties to Triggers. Add a new Combo trigger. In the Combo Actions, add the N buttons you want to press at the same time. Here you can also specify how much time they have to press the keys if you want to, but if you want it to be ‘instant’ (they MUST be pressed at the same time) you can’t set it to 0.0, do like 0.1 or something - experiment with it. Note: the order in which they’re added is the order in which they need to be pressed. Also, this should grey out the input key selection for your Combo.
(4) In your blueprint for IA_Combo, test for Completed, not Started. Testing for Started will fire when the first button in the combo list is pressed, which could be useful.
