The handy thing about using arrays for these inventories, is that Construct has a built-in action to sort an array. So, sorting the inventory is actually pretty easy – it takes a little bit of pre-planning, but it does mean you can simply press one key and the inventory is sorted.
If you look at the item information, you'll notice that all of the items are listed alphabetically. This is purely for sorting reasons – by arranging the items in a specific order in the JSON file, you can affect how they're sorted in the inventory.
When adding items to the inventory, you'll end up with an array filled with a set of ID numbers. If you want to then sort them, in this case alphabetically, all it takes is the following event:
This only sorts a single inventory category at a time, but if you disable the Inventory picking condition, all of your categories will be sorted at once. This can be done at any time as long as the inventory is open, so the player can sort their inventory whenever they get new stuff! And you don't have to sort alphabetically either, it simply depends on what order you put things into your JSON file.