Copy Inventory Item and Add it to HotBar

Hello folks!

I have my main widget(Game_HUD) which displays the inventory and some other stuff and I got another widget which displays my hotbar(HUD_Hotbars).

How would I go about this:
I pick up an item and this item is added to my inventory. Now I want to open up my inventory where my mouse cursor gets enabled and then go to the inventory slot where my picked up item has been stored, hover over it with my mouse and while hovering it I press a number(and only number strictly) and then the item gets added to the corresponding button number of my hotbar widget(or actionbar if you like to call it).

What is underlined I am trying to do.

What I’ve done till now experimenting with 1 button press:

So where do I go from here, any ideas?

Thanks in advance!