I've released the first, very much alpha, version of my chrome extension that adds various functionalities to the formula editor.
https://chrome.google.com/webstore/detail/better-formula-editor-for/lonibgccfehnjjhchfcbdhkaajhobeak
It's very much in alpha as there are some known limitations / quirks, but currently it highlights syntax errors, missing dimension errors, incompatible line item / formula data types and allows you to hover over a line item to see it's data type and dimensions. A couple of examples of how it looks below.
Hover to see dimensions:
Highlight data type errors:
Missing dimension warnings:
All the above are far from perfect; some of the error messages could be better but are a very basic first step. I'm also working on being able to hover over more things with data types (list items, list item properties, functions etc, not just line items), as well as things like function names to get the parameters etc.
Context-aware customised auto-complete for lineitem names / functions / module names etc is also on the list.
I'd be very interested in any feedback anyone has.
