I assumed by Advanced you meant the Advanced tab. It's already working :)

https://monosnap.com/file/1QYa5CjqUgQn06VL5XjgYE8dzMeuva

Can you show screen where it is?

I didn't write about Custom css area. Please, check carefully

https://monosnap.com/file/Bwy6UQUIEoKsGtaa95iadEnDCI5sLf

so I found that whatever css I add doesn't show up.

Why isn't it working? What am I doing wrong? on the screen you can see that there is no dot, I didn't put a dot there.

i try add class in Gutenberg Greenshift but nothing - https://mag.grafan.cz/tgb/

i try add class in Gutenberg Greenshift but nothing  - https://mag.grafan.cz/tgb/

you must add it to Class field

In Greenshift, it's Advanced - Advanced panel. In Elementor, it's in Advanced - Class

I also tried it in Greenshift and nothing. When I looked into the button code, I don't see the css. How is it possible it shouldn't be there when I add it to the css?

There is no dot. Where do you see the dot? I also added a screen where there is no dot. 

because you placed dot before class

?

I tried to put .act-rehub-login-popup into Elementor pro, Custom Css, but it doesn't work.

Can you please send me a screen, where exactly should I insert the .act-rehub-login-popup? Ideally in Elementor.

Thank you.

You can add class act-rehub-login-popup to button

And is there any way to make the login/registration popup open when a link or button is clicked?

Thank you

Settings - Buddypress - pages. Page where you have shortcode must be selected as your register page

Hello,

is it possible to add a registration/login box to the page? Or is such a page already prepared? Ideally it would be using Buddypress Shortcode, but it somehow doesn't work, it doesn't display the field.

https://codex.bbpress.org/features/shortcodes/

Account

[bbp-login] – Display the login screen.

[bbp-register] – Display the register screen.

[bbp-lost-pass] – Display the lost password screen.

Thank you