Metafield on product, more than 3 options not possible

I am trying to use metafields to enable customers to filter for options. I have a product where 4 of the options of the metafields apply, but after I add 3 options, the button add article isn’t clickable anymore.

If there would be a warning maximum articles then I would understand, but now I’m not sure what’s going on.

Can anyone (of Shopify) confirm that there is only 3 items possible or tell me how to add more.

Greetings,

Lucas