Sending emails with Flow is really useful. However, composing good looking emails with dynamic content is really difficult and tedious. The current UI experience here is really terrible. Microsoft - please consider the following improvements:
Add a better and more modern Rich Text / HTML editor to flow actions where needed. For example all actions for sending emails. Here we need a better experience for authoring the email body.
Allow authors to copy and paste HTML content including tags for dynamic content. This would allow for using an external editor.
Allow authors to edit text as Rich Text and as HTML source.