There have been a couple of attempts to create an application that allows users to hand draw chemical structures. Some rely on chemical structure recognition to convert the final structure into a chemical object, this obviously does not continuously update as draw. Others were probably limited because using a mouse as the input device was suboptimal.
ChemScribble looks like a well thought out chemical drawing package, whilst you can use a mouse it is clearly designed with pen/stylus input in mind. It is now available as a public beta (https://www.chemscribble.com).
ChemScribble is available for MacOS, Windows and Linux, For Mac users, ChemScribble works with an iPad in sidecar and an Apple Pencil. They are actively developing a web version of ChemScribble to make it even more accessible, and will continue to evaluate native iOS and Android applications as the project grows and user demand evolves.
