Is there a way, within the numeric value widget, to show the thousands separator (as the tag browser does) for an analog i/o tag?

6,512,342 is easier to read than 6512342.

I tried the CommaFormat function within a text expression, but it wouldn't let me hit "Ok" after putting an analog tag as the argument in the function.

No.

You can use basic text expressions to display the value, and then hide a 0.01 opacity numerical value linked behind it to the original to keep the ad hoc trend function and it'll kind of all look the same.

Generally I've found it's better to instead display like 6.51 M instead of 6,512,342 in your example though.

I thought about what you said and tried some workarounds.

I tried the CommaFormat function again, and it worked. I must have had a typo the first time.

Then, I put the text object into a tag widget which took care of the ability to click and bring up a trend because tag widgets have a nice way of doing that for you.

\System.CommaFormat(\Root\Value).

Thanks for getting the wheels turning.