I wanted to jump in here to let you all know that we are well aware of the desire for an expanded text area feature, and we have already begun discussions internally of how best to move forward with that and include it in a coming release.
As a little context, this release required a massive rewrite of the entire backend of the content builder to bring it under the same roof as the controls used in the header and footer builder. There are still pieces to include such as user defined presets and templates, but simply getting all elements across all builders was a massive undertaking.
That being said, part of reason why the text editor is the way it appears is due to the fact that this is the very same text control we've used in Pro's header and footer builders since their release, and we've never received any feedback on it being too small. Granted, we understand that the flow of working on large pieces of content is different than with headers, but you can rest assured you don't need to be concerned about the future of X or Pro. Every decision is weighed very heavily on all levels, and things that on the surface seem simple are often more complex than they appear. More importantly, we want you to know that you all are being heard, and we pride ourselves on listening to our community and responding as quickly as we can while weighing out all the needs and wants of every user. We certainly hear everyone on things regarding the text editor, and you will most certainly have a solution in place very soon.
Thank you for your feedback and understanding while we work through these items.