Why can't I hide the cursor with js or css and how to solve it (Anki for Desktop)?

[Eltaurus]

It’s probably the same Qt bug:

Mouse display issues in 2.1.57

This is a Qt bug that exists since 2.1.55. We do not know what causes it, sadly. Here’s the GitHub tracker: Duplicate of: [2.1.56] Mouse cursor on toolbar is inconsistent