Your comments

Yes, I totally understand what you mean. I plan to revamp the "+" button in Textastic to let you create a new, untitled text document.

Would it be ok if this always starts out as a plain text file (you can change the syntax in the File Properties popover) or should there be options for other kinds of files?

Ok, I'm glad that you found the problem.

Textastic 8 will have an option to ask for the password when connecting to (S)FTP servers.

Textastic 8 will support ECDSA and Ed25519 SSH keys.

Textastic 8 will allow you to select any installed monospaced font. You can use apps like AnyFont or Apple Configurator 2 to install custom fonts.

This will work in Textastic 8.