I'm trying to reduce the height of the text-field widget, I'm not able to reduce it below 34.
Is there any way to control it using CSS?
Read this article - ""Height" property of TextField in the TextArea widget does not accept value smaller than 34 px in ThingWorx 8.5": https://www.ptc.com/en/support/article/CS325213
Also a similar question was previously:
What version of ThingWorx are you running? From our testing it appears the 9.x versions of ThingWorx do not support anything less that 34 pcs, so if you need something smaller, you may need to create your own widget.
In your pic, did you use CSS to adjust the size? If so, there may be other elements such as font size, padding, etc. that would also require update in order for it to display correctly.
You can also submit this as a request on the ThingWorx Ideas Board.