@Bernard ,
Please see this older discussion, which links to issue#4566 – the developer does not believe there is room for a permanent zoom indicator on the status bar, so has rejected that request. There is no reason to believe he will have changed his mind.
That said, the older discussion I linked has links to PythonScript implementations that may be of use to you. If you’ve never used PythonScript, this FAQ explains how to take one of those example scripts and implement it on your computer.