LibreOffice Writer does not conform to conventional standards for shift-click. You should be able to both increase and decrease the selected text with a slift-click. This problem was first cited many years ago. Maybe the LibreOffice folks can do what OpenOfficeOrg has not done. This is much more important than a mere enhancement. This is a Writer problem, In Calc shift-click will both increase and decrease a selection.
"https://bugs.freedesktop.org/show_bug.cgi?id=41202"
This bug is marked as resolved But using Version: 5.0.4.2 Build ID: 2b9802c1994aa0b7dc6079e128979269cf95bc78 Locale : fr-FR (fr_FR) The problem is still there I have it changed to reopen
*** This bug has been marked as a duplicate of bug 41202 ***