Hi Sergio,
Thank you for picking up that ticket. Do you have any update on this issue? This new approach to richtext, however great, forces us to change all our text content if we can't get this syntax working the way described in the ticket.
Thanks

Hi JinFox,

With the Style based approach in Unreal RichText, the only way to modify the contents of a tag is to create a new Span derived class which performs any necessary operations on its child inlines.

I have attached an example of this, a Lowercase Span which will modify it's inlines, changing any Run Text to lowercase.

In order to use this Lowercase Span, you just need to create a Style with a Lowercase TargetType:
<Style x:Key="lowercase" TargetType="{x:Type local:Lowercase}"/>

This Style can then be used in RichText:
Hello this is <lowercase>LOWERCASE TEXT</>!

For your ChangeCase tag, you would create a ChangeCase Span with a Type dependency property, then you would create a Style for each Type:
<Style x:Key="camelcase" TargetType="{x:Type local:ChangeCase}">
<Setter Property="Type" Value="CamelCase"/>
</Style>
<Style x:Key="uppercase" TargetType="{x:Type local:ChangeCase}">
<Setter Property="Type" Value="UpperCase"/>
</Style>

Hi,
Thanks for this answer. This solution work for lowercase and uppercase example. I will open another ticket to do a request for supporting dynamic modifier like the ChangeCase example.
You can consider this one solved.