Hello @m0r0mete,
Thank you for contacting us, and sorry for any inconvenience that might have been caused due to that.
Long descriptions are not always preferable because they can exceed 160 characters. Since search engines like Google truncate any characters after 160 character limit, we added short description variable for that. But there are no limitations on that and we never force to use only short descriptions. You may use custom variables by adding filters too.
We tested the filter mentioned here in this URL, and it seems to be working fine on my end.
Please note that, you might not see the changes/preview on Snippet Editor, but you can always verify that by viewing your page source code. The description should be added there.
Can you please apply and check again in your source code to see if it’s working for you?
Looking forward to hearing back from you.