lyx [1] is great for live editing of latex . Set the instant preview Tools>Preferences>Display>Instant Preview if you want automatic latex rendering, although the editor rendering is nice as it is.
For something that is more of a calculator, SymPy [2] with sympy.init_printing() would be rendering latex automatically in any Jupyter notebook.
Specific tools I created for my own use for leveraging the above is pypad [3] together with calcpy [4] (%load_ext calcpy)
[1] LyX https://www.lyx.org
[2] SymPy https://www.sympy.org
[3] pypad https://github.com/idanpa/pypad
[4] calcpy https://github.com/idanpa/calcpy
Perhaps try purchasing a digitizer tablet with a stylus (e.g. Wacom's Intuos series) which will allow you to write your equations as you would with an ordinary writing instrument?