Try to select "XML" as the syntax definition in the status bar.

If you want better syntax highlighting, you can add custom syntax definitions to Textastic by using TextMate bundles. See

I'm just wondering: where is this necessary?

I wouldn't do it automatically, since for example Markdown uses two trailing space characters in a line to signal that the user wants to have a line break (<br>) after this line.

I think it would also be necessary to have an option to show space characters (and other invisibles) similar to how tab characters can already be shown.

Hello, you first need to select a target directory on the left side of the file transfer screen before the Download button becomes available.

It would be better to discuss this in a new thread or by email (support@textasticapp.com) as this topic is specifically for problems with Synology devices.

A screenshot of your connection settings and log files (Textastic log and server logs) might help.