Rich Text Editor can be configured to define the behaviour of the ENTER KEY. You use <p>, <br /> or <div> tags when you press enter. In either mode <br> tags can be created by using shift+enter.
<div class="mt-4"> <RTE:Editor runat="server" ContentCss="example.css" Toolbar="minimal" ID="Editor1" Height="150" EnterKeyTag="DIV" /> </div> <div class="mt-4"> <RTE:Editor runat="server" ContentCss="example.css" Toolbar="minimal" ID="Editor2" Height="150" EnterKeyTag="p" /> </div> <div class="mt-4"> <RTE:Editor runat="server" ContentCss="example.css" Toolbar="minimal" ID="Editor3" Height="150" EnterKeyTag="BR" /> </div>