I've got a Nintex form with a multiple line of text field with append option on. I would like to make the field higher but I don't know how. Any pointers?
Which field are you trying to make higher?
The appended text below the comments control?
If you are trying to increase the number of lines, edit the column in your list. You can increase the number of line for editing.
This control must be in your list for it to be able to append changes / additions.
So working on that assumption, go to your list settings (the list the form is based on), click on the column (looks like yours might be called comments request), then change the number of lines to more than 6.
In the form, simply drag the field larger. It really is as simple as that.
Once your column allows more than 6 lines of text (which is a lot to start out with), your field will be large enough to encompass it. If not, there is a scrolling feature included.
As for getting the previously entered text to show up higher in the form, I'm unaware of how to edit that portion.
If you are running into issues where you can not read all the text entered, try arranging your form so the field goes all the way across the form. It will auto resize to show everything and adjusts your other controls below it.