Chrome Remote Desktop with Windows 10 headless NAS, No Physical Mouse attached, Cannot see mouse pointer, Mouse emulator
Solution 1:
This is a known bug. A quick workaround (that you'll have to repeat each time you connect) is to click, hold, and drag the "Your desktop is currently shared" notification at the bottom of the screen. The mouse pointer will appear (but note that it won't change appearance when you hover over text or links etc).
Solution 2:
A solution I've come across is to go to Settings -> Ease of Access -> Mouse and enable Mouse Keys (move the mouse with the numpad). This enables the pointer and still allows the mouse to control it.