Steps to reproduce:
1) Open Creator
2) Go to options and set tab size to 4, for example
3) Create a new file.txt from the wizard and start typing
4) Go to options again, set tab size to 8, and apply

Result: Settings are not reflected on the current editor.

Notice that in this case the file is pure text (no code styles, C++ or QML, should have taken into consideration) and it's also not associated to any project (so global settings should take precedence).