how do i stack items up in inventory?

you need to also pick the text object to match the item uid ... or something that pairs the text to the object you create...

Edited: for example i mostly used local variables on objects... and do lets say item.orderid & text.orderid

if you have a dictionary or array with your item, you can also set that variable, and when u spawn the text object just feed the orderid of the item on the text orderid.

and then when u add a new item in your inventory pick the text that matches orderid with item.orderid

something like bellow code

repeat 5 create item at XY 
	set item.order id to loopindex
	create text at item.X item.y + 10
	set text.orderid to loopindex
on click add to array item.atorderid + 1 
pick text.object by evaluate text.orderid = array.at(text.orderid) set text to array.valueAt(text.orderid)