Mathcha is described as 'We want to help people to quickly write any mathematics formula/equation. People don't need to know about LATEX, but still have a powerful and rich Mathematics symbols/layouts/features so they can share with others' and is an app in the Education & Reference category. There are five alternatives to Mathcha for a variety of platforms, including Mac, Windows, Linux, iPad and Apple iWork. The best alternative is MathType. It's not free, so if you're looking for a free alternative, you could try diagrams or LaTeXDraw. Other great apps like Mathcha are TeXmacs (Free, Open Source) and TikZiT (Free, Open Source).
MathType is a powerful interactive equation editor for Windows and Macintosh that lets you create mathematical notation for word processing, web pages, desktop publishing, presentations, elearning, and for TeX, LaTeX, and MathML documents.
LaTeXDraw is a graphical drawing editor for LaTeX. LaTeXDraw can be used to 1) generate PSTricks code; 2) directly create PDF or PS pictures. LaTeXDraw is developed in Java and thus runs on top of Linux, Windows, and Mac OS X.
GNU TeXmacs is a free scientific editing platform designed to create beautiful technical documents. It provides a unified and user friendly framework for editing structured documents with different types of content: text, math, graphics, slides, etc.