You're right that you can't do collision detection on text objects.
If you just want to add extra text you can use the "append text" action in the text object, and use '& newline'.
If you want to add a new text instance and position it next to the other, assuming you have the origin point on the top left, you can pick the text object and then create another text object at X=text.BBoxLeft, Y=BBoxbottom+20.
This will create another text object 20px below the one that is picked.