D11599 adds a magnifier to the rectangular region selection screen, but
the corresponding help text on how to toggle the magnifier temporarily
is a bit hidden: Most users won't discover a mouse-over help text on a
checkbox in the config dialog.
To make the feature easier to notice, the corresponding text is added to
the on-screen help. As a prerequisite, the very long line of text is
first broken up into a more tabular style.
The second help text is also broken up and reworded, as well as adapted
to the default border style.
Setting the default visibility of the help texts to `false` avoids
showing them initially for a brief moment.