No warning for recharging mouse and keyboard!

There may be a reminder at 10% or 20% (don't know) but I put a recurring reminder on my calendar to recharge them once a month. Works for me and gives me time to recharge them as time allows after the reminder.

Also see: Low-Battery Warning for Apple Magic Mouse… - Apple Community

All you need is to have the Bluetooth icon show in the upper right of the display, hen you can check whenever you want.

I use to get a notification in top right corner of screen but no more for some reason. Just have to keep an eye on the charge.