Allow custom inline formats in writer field

The new WYSIWYG fields are a great step forward, especially for casual editors, who don’t write everything in Markdown. But in some of my client projects, there are additional requirements for text formatting.

A typical scenario would be colored text in a multiline headline. E.g. the first 2 words should be formatted in a different color or some arbitrary words within a text block should have a different formatting. Another example is the <mark> element, which comes in very handy for documentation and scientific texts.

In Markdown, it’s very easy to add an additional formatting command using regex or use the <strong> element, as long as other bold text is not needed. A better and more flexible solution would be the possibility to define custom inline formats for the editor. Either using blueprints of as JavaScript extension.

The latter approach would be way more complicated for the developer, but would offer the possibility of having advanced button such as special link types, inline images etc.

v4 will support custom marks and nodes for the Writer, which gives direct access to the powerful capabilities of prosemirror. I would consider that these extensions meet this suggestion.

It would also be great to add an option to the link button to set internal links.

@John-David Deubl I don’t think this relates to this suggested idea, but https://kirby.nolt.io/268