Dealing with typing archaic letters to get a specific date/time pattern is just wrong. And a link to a PHP manual is not the answer... unless you're a programmer.
Some options - there should be a list of common examples on that page (e.g. how do I add am/pm) - Replace the PHP.net tutorial link with one on bdcms.org that explains it better - get away from having the user deal with PHP stuff. Provide some kind of drag and drop or GUI to help. Not sure what at the moment.
This always takes me time to figure this out.
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A simple way — use Field Group to create a container for fields https://backdropcms.org/project/field_group and CSS Flex оr Grid to alignment.
Layout also for /node/add/ forms?
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Prevent Backdrop from sending emails
The short answer is no, you can't theme forms or change their layouts through the UI. There is a ported version of Display Suite, which has a submodule called Display Suite Forms that allows you...
Layout also for /node/add/ forms?