This didn't work
Yep it's possible.
You need to convert your form to html instead of xml.
Create a dashboard, then go into it, click edit and convert to html. From there you can continue modifying the html to suit your needs.
Then, you can use something like the following to change the label:
old:
new:
I've just tested it and it works perfectly.
Which Splunk version? Simple or Advanced xml?