BlockNQC

Visual programming editor to generate NQC code which can then be compiled with a NQC compiler, e.g. WebNQC embedded into WebPBrick.

Blockly

Check Blockly Block Wiki: https://github.com/google/blockly/wiki
Check Blockly Advanced Playground: https://blockly-demo.appspot.com/static/tests/playgrounds/advanced_playground.html
See also: https://github.com/google/blockly-samples/blob/master/plugins/dev-tools/src/toolboxCategories.js

Use Blockly Developer Tools: https://developers.google.com/blockly/guides/create-custom-blocks/blockly-developer-tools > Block Factory https://blockly-demo.appspot.com/static/demos/blockfactory/index.html
https://blockly-demo.appspot.com/static/demos/blockfactory/index.html

Can the number of variables be limited? (All variables are made global, so they are limited by the RCX bytecode interpreter to 32. Blockly treats variables as global by default.)
Can the number of options of built-in blocks be reduced? E.g. ^ (JavaScript code generator generates Math.pow()) be removed from math_arithmetic?
How to implement the task feature properly? Only tasks should be started/stopped that exists (i.e. where their name has been declared).
How can the way of storing/loading programs (as JSON) be improved?

(considered nice-to-have)

Implement Program() and SelectProgram()
Implement functions and subroutines (code blocks can be copy-pasted).
Support for loops
Support switch statement
Implement resource access control (acquire, monitor)
Restrict math_single block to abs() and unary minus (or reimplement)
Reimplement math_number_property
Add support for sign() and bitwise operations
Implement OutputStatus()
Support counters
Support events
Add instructions (context-aware tooltips)
Add support for "RCX2" functions - need to double-check against used firmware version?!
Define aliases for sensor inputs and (motor) outputs.