Where exactly do I find this feature in Sublime Text?

For local preview, Textastic doesn't use http but its own preview protocol (urls internally start with "preview://"). So you need to specify the http protocol since it would otherwise try to load the URL using the preview:// protocol which is only for local files.

This is very similar to the "file://" protocol for local files in desktop browsers. 

This should already work. Can you show me the code you're using?

Currently, only the $UUID variable is supported. It automatically creates a new uuid and inserts it.

I'll consider adding more variables in the future.

You can discern folders from files not only by the icon, but also by the gray chevron on the right side of the folder name and the fact that it doesn't have a time stamp and file size.

Safari uses very similar icons with the same color for folders and bookmarks in its bookmarks list.

I don't plan to change that sorry. 

Yes, you are right. Remote file information is only saved when there was no error during the upload. This will be fixed in the next update.

Unfortunately, the transition to 64-bit in the latest version of Textastic introduced a bug on 32-bit devices (i.e. everything but iPad Air, iPad mini Retina and iPhone 5s): on these devices, the file size is passed incorrectly to the FTP library.

In my tests, the file was uploaded correctly, you would just get the "partial upload" error message. You can ignore that.

This will be fixed in the next update. I'm very sorry for the inconvenience.

I can't seem to reproduce it anymore even when repeating operations, sorry.

Are you doing the same as shown in your video, but just several times or are you doing something differently?