Problem

Rich text editor doesn't support custom elements. This can be achieved by extending the Rich Text editor or extending Markdown to suit your requirements.

eg a link which opens login modal inside running rich text. While plain links are possible, these custom links are only possible if a custom entry can be embedded inside Rich text.

Similarly, embedding links which open in a new tab inside a rich text snippet.

Solution

While creating a rich text field, a setting can be enabled to embed entries and which content types are allowed to embed.

Embed can be inline or block level or both.