Perhaps using layers will do what you need.
Create a new layer and move your note entity to this layer.
When the text isn't needed, turn the layer off (light bulb in the Layer dialog is off [not yellow]).
If you use this often enough, you may want to display the Layers toolbar.
To make a watermark note:
1. Right-click in a blank area of your drawing and select "Edit Sheet Format".
2. Insert the watermark Note.
3. Right-click on the Note and select "Display Note Behind Sheet".
4. Afterwards, right-click in a blank area of your drawing and select "Edit Sheet".
IS SO GOOD YOUR ANSWER.
I GUESS THAT IS A MISTAKE.