Hand-drawing the equations, like you would do on Zoom's whiteboard, is not great. We all have mouse & keyboard interfaces, and mouse-drawn square-root symbols and subscripts leave a lot to be desired. Also, we copy and paste equations and modify them. The whiteboard interface has a struggle with this as well. The mouse-drawn stuff tends to be too large; we can't fit enough on screen.
What tool would you recommend for this scenario? A bonus would be to have something like a mini Desmos calculator on the side, where I can drop (in)equations and get them rendered.
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