I-Firefox Isithangami Sokwesekwa

I searched in Google and this website for instructions for how to delete specific cookies for a website. Many instructions are probably for older versions of Firefox.

I used to be able to login as of this morning to Wizzair.com. Then suddenly, regardless what I do, I can no longer use Firefox to login. I used the Preferences/Privacy & Security/Cookies & Site data/Manage Data for Wizzair.com to remove the cookies for the website, but it didn't help. I changed the password, it didn't help.

Their chat support sent me to their Privacy statement. There, there is custom list of cookies that they use. I was told to try to delete them individually... I have no idea how to do that and I could not find a method that works.

I can login the website using Safari. Any suggestions for what to do to be able to use again Firefox to login into this website? Thanks in advance.

Looking for a way to add about 50 sites to the list of exceptions Firefox->Preferences->Privacy & Security->Cookies and Site data [article on managing cookies and site data doesn't suggest it is possible.] Any help is much appreciated:)