OK. Just imagine I still want to upload some images. But they need new Keywords to have any sense at all.
Any idea where I request these now?

You need to go to Account Management > Contact Us
Then choose My Online Content and Suggest a Keyword.
Seems that the logical option of My Current Submissions doesn't give you the subcategory of Suggest a Keyword, you have to have the content accepted before you can ask for a keyword to be added. Doesn't make much sense, because if they choose not to add the keyword, you'd then have to ask for the content to be removed, if it was the actual subject.
Ho-hum, can't waste time trying to work out their reasoning.

BTW, you'd have found the answer on iS's forum, and sooner.