Faye,
I also need the thousand separator to appear with in user-input fields as well.
I donāt think you can have it in the Input element itself right now, but as a workaround you can place a text element beneath the Input in this way:
Then in the preview mode it will look like this (and adjust as the User changes the value of the Input)
Faye, this looks promising.
Let me test it in my app!
I ended up addressing my issue with a workaround:
When the account admin first sets up their account in my SaaS, they are taken to a Settings page and they select their currency of choice.
This way, I can use the ācurrencyā type in the appropriate user input and display fields of my app.
The only problem is that I have other fields which display numbers but which are NOT currency numbers. Those fields wonāt display commas. 
That sounds like a great solution 
You can display numbers with commas by using the āformatted asā option in the dynamic expression (As long as the Numbersās data type is Number and not Text, the Number Formatting window will appear):
