Incorrect hotkey "Shift+F4" here and offline manual. https://help.libreoffice.org/Calc/Addresses_and_References,_Absolute_and_Relative/en this hotkey don't work in last release 5.3.4.2 and here is true, "F4", this hotkey is worked https://help.libreoffice.org/Calc/Shortcut_Keys_for_Spreadsheets/en
Indeed, it is written as Shift+F4, but it should be F4: https://opengrok.libreoffice.org/xref/help/source/text/scalc/guide/relativ_absolut_ref.xhp#49
liongold committed a patch related to this issue. It has been pushed to "master": http://cgit.freedesktop.org/libreoffice/help/commit/?id=6c20b138bbf088d5f2a11cd1143c1d084c9c27af tdf#109213 - Changed hotkey for switching between absolute and relative referencing