I find it annoying that the Mac app doesn't behave as per the standard macOS document model. When I want Textastic to run the way it does on iOS, I'll grab my iPad.
Specifically:
Add an option to hide the tab bar
Make the Cmd-N shortcut open a new window instead of a new tab
Documents opened from Finder open in a new window instead of any existing one.
I don't think it even needs a checkbox in the preferences, just hiding the tab bar should enable items 2 and 3 (and persist across app launches).
Is this still on your to-do list?
I find it annoying that the Mac app doesn't behave as per the standard macOS document model. When I want Textastic to run the way it does on iOS, I'll grab my iPad.
Specifically:
I don't think it even needs a checkbox in the preferences, just hiding the tab bar should enable items 2 and 3 (and persist across app launches).