In a figure in draw.io, I have arrows pointing basically everywhere. When I LaTeX-format the "label" in a "connector with 3 Labels" object, the formatted text is given a fixed border, which I find impossible to change. Below is an image of the label with its borders illustrated: 
The thick, outer border is changeable, no problems there. I can go into the Style menu on the right-hand side and choose all sorts of options for the outer border.
The thin, inner border originates from giving the LaTeX-formatted $$(1,3)$$ text the property of "Background Color" and "Border Color" in the Text menu on the right-hand side. This is mostly for illustrating how the inner border looks.
The problem: For the life of me, I cannot change this inner border's geometry. It clips with every object it is in front of, and if I don't have a clipping border at all, it is still just awful for my figure. I need to change the inner border's geometry, make it a circle, triangle, whatever. I just need to find out how to customize it.
