You are going to kill me! But i finally found this link https://www.defold.com/ref/label/ and was able to use metrics[width] and make two labels, the second one changing position dynamically according to the width of the first one’s text (previously i was sure I could only get the label size, which is here https://www.defold.com/manuals/label/, rather than the text width).
Still, I learned about GUI scripts, which I had never used before, and also, I learned a little more about lua, which is always handy.