I searched for simple methods to do something similar to this and found these posts. Anyone who has better ideas, you are welcome to reply.
Hide Mouse
I found that the widget also affects cursor visibility, not only the player controller. This was why I couldn’t hide my mouse even if I used ‘player controller-set show mouse cursor’.
Easy fix! - losing UI focus on mouse click
This guy suggests to make a huge invisible button covering the entire screen. Whenever this is clicked, the ‘on-click’ event will make focus on the menu buttons again and prevent losing focus from the menu buttons. Clicking anywhere on the screen will lead to clicking the screen-sized button and trigger the ‘on-click’ event of it.
So I hid my mouse cursor from the widget blueprint’s panel settings, and made a screen-sized invisible button in order to force my focus on the menu buttons no matter where I click.