I think AzDude thinks you are on Windows 11.
On Windows 10 you go to the same place but are offered three options. Left aligned, Centre aligned and position the taskbar buttons in the centre of the taskbar.
You want centre aligned not position the taskbar buttons in the centre of the taskbar.
Be aware that if you have Stardock Curtains you must ensure you have the very latest version installed or it will not work.
Hi - thanks for the reply. As you can see from the screen cap just posted - I am already set up that way. The taskbar buttons align centrally, but the Start Menu is still lined up on the left side. If I set that same dropdown to "center aligned" the start button moves towards the middle of the taskbar, but when the menu is opened, it is still right below the start button, but now moved more to the center. See this screen cap:

No matter what settings I use, I cannot get the start menu centralised on the screen, as it is in Windows 11 and also on the Start11 website (see below):

I notice that they only have 7 icons on the taskbar, so it looks centred but isn't really. Nor is this how Windows 11 works, where the start menu is centered no matter where the start button is located (ie to the extreme left). I bought Start 11 principally for this feature, so if it only works with 7 icons on the taskbar, it doesn't really do what I thought it did.
Any ideas gratefully received and thanks for the help so far.
Zed