It was a typo error. It shoud be:

display: none;

Thanks @LeonidS. I already know that css code. I am not talking about hiding it on mobile devices, i meant in the Mobile App. I would like it to be displayed on the phone (when using a website browser on the phone), tablet and desktop but not in the mobile app, similar to the setting we have for Navigation Items:

Hidden on:

phone

tablet

desktop

-> mobile app

Thanks

Hi @LeonidS@LeonidS, I have found the answer to my own question by mysefl.

To hide it on the mobile app, the following class attribute should be added to the tag/element

bx-def-mobile-app-hide

For other devices, these ones should be used:

To hide on the phone:

bx-def-media-phone-hide

To hide on the tablet:

bx-def-media-tablet-hide

To hide on the desktop:

bx-def-media-desktop-hide

and it works.

Additionally, the following class attributes can be used:

To display something to guest only:

bx-hide-when-logged-in

To display something to members only:

bx-hide-when-logged-out

Update:

To apply a css style to visitors/guests only, use (thanks to LeonidS):

.bx-user-unauthorized .my-element {
your style here;
}

Thanks