
Ah, right. I start calibre via an icon on the taskbar which pointed indeed to calibre.exe. (it even says so...)
On removing that, recreating the icon for calibre_portable.exe and activating it, a 2nd (pinnable) icon on the taskbar appears for calibre.exe. So I guess in the past I must have removed the wrong calibre icon in some attempt to clean up duplicate icons.
Thanks.