What are input tags in GAS and why you should use them
Input tags are one way of activating gameplay abilities in GAS. They allow you to easily tie any gameplay ability's activation input to a specific gameplay tag, instead of hardcoding bindings. If you're new to gameplay tags, my earlier post covers them.
Input tags also let you rebind or assign abilities at runtime without touching input code.
How to add an input tag to an ability
The way input tags are added to abilities is by accessing that ability's spec, and adding your input tag to its dynamic spec source tags, which are just an FGameplayTagContainer . They are carried over with that ability's spec, and can always be accessed if you have that spec.
