A matter of fact that, ERPNext is the most flexible ERP platform ever from customization points of view among others by considering the non-IT skills GUI allowing adding custom fields and forms as well, BUT!
Yet annoying while dealing with some basic mathematical calculations such as and not limited to, areas, volumes or any general simple combined multiply/division operations using existing and/or custom fields as inputs.
Please enrich customization capabilities by considering the simple needs of end-users DOES NOT care about client-side vs server-side scripts to simply input X and Y values and looking for auto calculate Z = X*Y in child table along with some other basic SUM, COUNT, AVERAGE, etc. functions in parent tables by introducing predefined elements using field names as inputs.
the community is happy to received PR. Maybe you can start one.