There is a bug in Logi Options+ customization for my Performance MX mouse. I use since decades the Enter keystroke assignment on my numerous Logitech mice I bought in my life. It saves a lot of time to click enter onto an alert in the top left corner while having the mouse in the bottom right corner of the screen. Logi Options 1.58.484418 does not accept the Enter key for a customization of the mouse buttons. This is clearly a bug. Note, until fixed, I will have to downgrade from Logi Options+ back to Logi Options. Note also: So far none of the Options software has ever surpassed the power of Logitech Control Centre, which has served me well for decades. It is time Logitech programmers catch up to previous excellence ;-).