Keyboard shortcut [V] not disabled for elements that can't be saved as invisible
It seems that, if you make a bracket (curly bracket or otherwise) invisible in a score, this is not actually kept on save.
1) Create a new score.
2) Make one of the curly brackets about one of the staves invisible.
4) Quit, re-open, and load the save
Expected: the bracket that you set invisible remains invisible
Actual: the invisible bracket is now visible