The Start Menu in Windows 10

[Guzeppi]

Have lost the arrow which is used to open the Start Menu in Windows 10.  How to
 retrieve it, please?

Many thanks in advance.

Guzeppi

[Mark.]

do you mean the mouse pointer???
have you rebooted the PC?

but for your particular problem, hitting the Windows key on the keyboard will also bring up the Windows 10 start menu (if you haven't installed a 3rd party start menu replacement software).
then you can use the keyboard to navigate to whatever you were after.

[Salmon Trout]

Some laptops have a "hide the mouse pointer" feature which is toggled by a function key or keys which you may have pressed accidentally.. Toshibas may use F5, Asus may use FN + F5. Tell us what machine you are using. The key may have a picture of a mouse with a line through it.