Thank you for implementing this! Fantastic improvement!

@Prowl - We discussed creating a separate expression editor panel, but chose not to take on that additional work. It's something we are still considering for the future.

There is a separate UserVoice request for an expression editor panel, you're welcome to vote and comment on that to help raise it's visibility:
https://adobe-video.uservoice.com/forums/911311-after-effects/suggestions/33990229-expression-editing-window

Great that this is completed... but why is not in a separate dockable window... not in the timeline which is just annoying - could have a list on the left with all expressions in a project and you can access and change them quickly,

A place to edit the text that isn't constrained by the timeline panel, line numbers, syntax highlighting, more descriptive error messages and easy, contextualized access to documentation on the library would be AWESOME.

One place I very often get stuck is trying to target a specific field, some times from other layers. A more intuitive way to call these other properties would be great.

Like most comments :

1. Better Debugging (Line numbers, syntax error highlight, and better runTime error messages)

2. AutoComplete (for layer/property names more than javascript)

3. Colors

4. Separate Panel (although it's not obvious how. As is now there is the possiblity to view several expressions at once, which is good too).

The houdini VEX editor isn't too bad, check it out for some good ideas.
And most importantly, make links to documentation (and while we're at it - update the documentation to be more useful!). As a semi-professional programmer who has written a few full applications by myself I can tell you that documentation is EVERYTHING when programming and the more work you do to make the documentation useful the better. If you have a dedicated editor this provides plenty of opportunity to improve this experience!

• An easier-to-use window - either pop open into another panel or auto size so it isn't so hard to navigate
• Ability to search/replace in expressions
• Library to save/paste common expressions
• Line numbers
• Auto-complete layer names
• Better de-bugging
• All the other comments people have mentioned about font size, colors, etc.

Apart from the obvious, proper debugging is much needed!

Having the 'library' available on right mouse button click (i.e. the list of objects and properties which is available from the little right arrow next to the expression pickwhip) would make a phantastic companion to auto-complete.

A debugger panel that can step through and show the current values of variables and properties would be a great thing to have as well.

Most important thing to add is monospaced typeface, correct identation and colour coding (even if its just like JS). It's really hard to read code when it's not monospaced. Line numbers would be great too.

The suggestion of autocompleting layer names and functions would be incredible.

Seperate window would be cool but I'd still want to be able to edit expressions within the timeline.

A separate window for entering code, so we aren't limited to moving around the timeline and stretching the entry area up every time we want to code.

Maybe something like an "effects window" but for expression script? When you click a property that has an expression, the code would pop up?

Color scheme with highlights, autocomplete - for example, type thisComp.layer ("F and a selection of the layers starting with F will appear, as with all other commands.) I personally do not have a kind of debugging, so I always have to build help effects in order to show values ​​to me, especially in the development very time consuming.Now, if I want to know what value the variables a and b always have at the end [a, b] ;, but when I'm in the rotation, I have to I first [a], and then in a second attempt [b]; spend. Likewise a template option as in the effect area. Often, you have to copy good source code from other projects together. Line numbering also makes sense, because you first with error messages I currently write Expression only in Notepad ++ and then copy the source code into After Effects.

I'd want this order for features

1. Numbered Lines
2. Syntax Highlighting
3. Monospaced font
4. Auto-Complete

Color coding and auto-complete would be great.

Slightly going off on a tangent, it would also be great to have a script input "terminal" to just type in quick scripts without having to use ExtendScript Toolkit

Same as mentioned. To the very least : line numbering, colors, auto complete, bigger cleaner font

Line numbers (much easier if an error can point to a line), syntax coloring, auto-complete, etc. are all good suggestions. Larger font would be nice too, but having a monospaced font would be even better (and might appear larger visually even if it isn't actually larger).

1. A file/project explorer for previous templates
2. Intellisense(auto completion that is scope specific)
3. Color coding for different types(variables, classes, keywords, etc)
4. A linter to catch logical errors
5. Support for customizable shortcuts
6. Unit Testing

I would like the ability to choose font and size, a GREY ui with syntax coloring, but most importantly, smarter handling of the text frame (push layer to top of timeline, auto expand expression to at least 10 lines, expand with typing, etc). For complicated things, rather than build another text editor in AE, could you just sync with sublime or brackets or some such?

Line numbering, auto complete library, color coding. Basically, make it Sublime Text.