stan wrote: Mon Jan 25, 2021 8:54 pm
I followed the links and the results are as in previous post.

This what is missed and I can't fix that.
... That is a heading ... it is not bolded, that is why you cannot select it (the red separator is a heading separator.)
Maple Mini is the 1st board selection under the STM32 Boards (Stm32duino.com) heading.
A single core can have one or many individual boards selections. The Arduino IDE parses the selections from the boards.txt file.
The IDE builds the Boards menu dynamically from installed (or /Arduino/hardware) cores. Dynamically means each time the IDE is opened by the host OS. The Menu will also refresh when new cores are installed through the Installation menu.
The Examples that get installed with the IDE may look like:
https://www.arduino.cc/en/Tutorial/BuiltInExamples
I say "may" because the IDE changes quicker than the documentation. I do not wish to be rude, but the IDE is ever-changing and there is even a pre-release people can install. Add to that even though it is JAVA based, there are numerous ways it gets installed. Bottom line, there is no absolute guarantee that anyone will get two identical installations, but generally the same features that matter will appear between recent installations on OS-X, Linux, and Windows.