The following paragraphs in Help are outdated: Displays the current selection mode. You can switch between STD = Standard, EXT = Extend, ADD = Add, BLK = Block selection. Each click in the field cycles through the available options: Display Mode Effect STD Standard mode Click in text where you want to position the cursor; click in a cell to make it the active cell. Any other selection is then deselected. EXT Extension mode (F8) Clicking in the text extends or crops the current selection. ADD Additional selection mode (Shift+F8) A new selection is added to an existing selection. The result is a multiple selection. BLK Block selection mode (Ctrl+Shift+F8) A block of text can be selected. The thing described no longer exists like that: it is replaced by an icon. Clicking no longer cycles, but opens a pop-up menu to select the desired selection mode.
Andras Timar committed a patch related to this issue. It has been pushed to "libreoffice-3-6": http://cgit.freedesktop.org/libreoffice/help/commit/?id=dd3b86787d441b8b84e89cb25c61170ec8cf121d&g=libreoffice-3-6 fdo#51416 update of selection mode help page It will be available in LibreOffice 3.6.
Andras Timar committed a patch related to this issue. It has been pushed to "master": http://cgit.freedesktop.org/libreoffice/help/commit/?id=81739d09450d94e3a68b70903341f1127b145441 fdo#51416 update of selection mode help page