I have created two global product attributes: "Select Colour" and "Select Worktop" in that order.
I can only add the Colour Attribute to a Variable Product.
It wont allow me to also add the second attribute, "Worktop". If I click "add" nothing happens, no errors, etc. it just wont add it.
Both global attributes are configured correctly.
It only allows me to add a custom attribute in addition to "Colour".