@crob
As other mentioned if you want customized display message box, you can use "Display custom form".
1. First search "Display custom form" in action panel and drag/drop into workspace. Then click on the custom form designer

2. Then it will display a designer form like the one below, where you can design your forms with the required controls.
Assuming you have some lengthy text stored in a variable called varDisplayText and you want to display that message in a message box. Here, I have included a text block and a submit button in the custom designer.
For the text block, as highlighted in blue, configure your variable name(varDisplayText) in Text parameter and set the height to Stretch, then check the wrap option.

3. If you prefer to maintain a minimum height for your message box, simply click on the white area below the submit button. This will reveal the settings for the form, allowing you to adjust the height in pixels. For instance, I have set it to 400 pixels, and you will see the same reflected in the preview form.

Then click done and save the custom form and run you will get form like below:

Thanks,
Deenuji Loganathan 👩💻
Automation Evangelist 🤖
Follow me on LinkedIn 👥
-------------------------------------------------------------------------------------------------------------
If I've helped solve your query, kindly mark my response as the solution ✔ and give it a thumbs up!👍 Your feedback supports future seekers 🚀