Oh, and for new templates to be picked up by Textastic, you do not need to restart the app. It's sufficient to just add a new file and select the template.

Ah, ok. My answer above was for adding syntax highlighting support for .mxml files. I didn't realize you wanted to add a template.

You need to json-encode the snippet string. So in your case, you need to escape the quote characters and newlines. 

Replace " with \" and newlines with \n

It would something like this:

snippet = "<?xml version=\"1.0\" encoding=\"utf-8\"?>\n<s:WindowedApplication xmlns:fx=\"http://ns.adobe.com/mxml/2009\" \n                       xmlns:s=\"library://ns.adobe.com/flex/spark\" \n                       xmlns:mx=\"library://ns.adobe.com/flex/m\""

What exactly does not work?

You can add your own TextMate-compatible syntax definitions to Textastic. Have a look at the manual: http://www.textasticapp.com/v4/manual/lessons/How_can_I_add_my_own_syntax_definitions__themes_and_templates.html

You can find a Flex TextMate bundle with an .mxml language definition at https://github.com/simongregory/flex-tmbundle

Sorry, but Apple doesn't allow compilers or interpreters in apps that also allow file downloads and file sharing.

Sorry, but I don't speak Russian. Can you please post in English (or German)?

It would sure be nice, but I think it would be out of the scope of Textastic. But it sounds like a good idea for a new app.

The cursor movement happens instantly, but the the scrolling happens after a very short delay. This is not only when using external keyboard, but also when you move the cursor with your finger.

I'll consider improving the behavior.

Just tap on the blue "Search" button to dismiss the keyboard. Then you can tap on the "Done" button.