Refer to screenshots, there is a multiple line custom field but I can't find it from the dropdown when I need to get it from dynamic source. Please advise how.
I believe that multiline fields aren't allowed to be added as dynamic content for inline dynamic texts. In this case I would recommend that you use the single field block to add the dynamic text rather than using the inline dynamic text option.
I suspect that this will be the same for WYSIWYG fields as the volume of content that they can provide.
The classic editor doesn't use dynamic content. If you switch to the classic mode for the content template then you will need to use the shortcode for the field.
You also have the option to use the shortcode block to manually add the shortcode for the field to the location as well.