--f7-block-padding-horizontal: 0px reduces left and right margin --f7-navbar-height: 0 is only required for iOS stylesheet is required to inject css to overwrite app.css styles. in this case top margin
I tried it on my system but it does not seem to work. On desktop screens I don’t care as it is barely visible. But on my iPhone it looks like this (cards of custom widget moved away from top and out of center):