I use logseq for my chemistry notes and KaTeX and MathJaX have an extension for rendering chemical equations.
Here it is: Manual for: mhchem for MathJax, mhchem for KaTeX
Most other places that use katex or mathjax have this enabled, notion, typora, stack exchange etc.
If this could be added that would be great 
this would turn
“$2H_2(g)+O_2(g) \rightarrow 2H_2O(g)$”
into
“$\ce{2H2(g)+O2(g)->2H2O(g)}$”
The bigger the equation the greater the improvment
This has apparently been solved for ages now.
As seen here: