There should be an option to create a new shop/gallery at the bottom of the page, with a text box for the shop name, a drop-down menu where you can choose a shop or gallery, and a blue "Create Shop" button.

If you're not seeing those options, please try making sure that you are on the most recent version of Firefox, and that you don't have any extensions that may be blocking it!

Have you checked your security settings and your extensions to make sure that nothing's blocking it? I'm using Firefox and see the shop creation menu just fine, so I can't replicate what you're seeing.

Have you tried clearing your Internet browser cache "for all time" and then tried again after checking your extensions and disabling anything that may be blocking the menu from appearing?

This should be fixed now, and has details in his post here:

https://subeta.net/forums.php/gotopost/67946794