Thanks for the logs, I'll try to reproduce it.

How exactly did you create the new file and where did you save it? Did you use the "Create External File" command while offline?

(I don't use OneDrive myself, but I heard a few times that the OneDrive file provider is not very reliable.)

I can only point you to the Sublime Text documentation on syntax definitions at https://www.sublimetext.com/docs/syntax.html 

Please note that Textastic only supports the features of Sublime Text 3.0 syntax definitions, not later ones.

Maybe you can find a TextMate 1 bundle or Sublime Text 3 package of a language that is similar to Batari Basic and modify it?

Hello,

how did you download the TextMate bundle from GitHub?

Please try the following:

• go to https://github.com/nitaigao/racket-tmbundle in Safari on your iPad
• tap the green "Code" button and select "Download ZIP"
• Unzip the file in the Files app
• Copy the folder "racket-tmbundle-master" to "On my iPad/Textastic/#Textastic/"
• In Textastic, rename the folder to "racket.tmbundle"
• Go to Textastic's Settings -> Other and tap "Reload Customizations"

Now "Racket" should be listed in File Properties -> Syntax Definition after opening a file.

Yes, you are right. Currently the drag interaction of a tab (which can be used to create a new window from the tab) interferes with the reorder gesture when using a mouse or trackpad. So this means that reordering tabs currently only works when using your finger to drag tabs.

I'll see what I can do to make it work. 

Textastic 9.8.7 now uses MultiMarkdown 6 and supports file transclusion: 

Use {{some_other_file.md}} in a Markdown file to include other Markdown files.

See https://fletcher.github.io/MultiMarkdown-6/syntax/transclusion.html for details.