Planned/In Progress Shop Cart Amount isn't decreasable and buttons are irritating

[Gummibeer]

I wanted to buy a thread highlight for PHP turned 25 years 🎉.
After adding it to the cart I've clicked on "purchase" instead of "checkout" - this added a second one to my cart. Now I can't checkout because I can't remove the second one from my cart. 🤔

RFC:

• rename purchase button to add to cart
• add an option to remove items from cart - in it's whole and/or decrease amount
• add an option during thread creation and in thread view to promote it
• is there a reason why only author can promote? Couldn't it be used like a voting system by the whole community?

for this I think that it would also be more convenience if I have an option in the thread to promote it, popping up a modal asking me to invest 100 credits and if I approve do everything - remove 100 credits and promote this thread. Right now the whole way feels a bit clunky and irritating.
Create thread, go to shop, buy the item, go to inventory(?), use the item(?).