Qt Creator has a function, "Edit" > "Advanced" > "Auto-format Selection".

For *.cpp files, this function can format the selected block only, while leaving the rest of the file untouched.

qmlformat currently only operates on the whole file. It would be nice if it could format, for example, the currently-selected JS block without touching the rest of the file. Then, qmlformat can be used as the backend for Qt Creator's "Auto-format Selection" function.