Here are some keybindings I use for window control on Lubuntu/LXDE. The first binding is what you're searching for but I thought you might find the other ones useful as well:

<!-- Keybindings for window tiling -->



    <keybind key="C-W-Up">        # FullScreen

      <action name="Maximize"/>

    </keybind>

    <keybind key="C-W-Down">        # MiddleScreen

      <action name="UnmaximizeFull"/>

      <action name="MoveResizeTo"><x>center</x><y>center</y><width>50%</width><height>50%</height></action>

    </keybind>



    <keybind key="C-W-Left">        # HalfLeftScreen

      <action name="UnmaximizeFull"/>

      <action name="MoveResizeTo"><x>0</x><y>0</y><height>100%</height><width>50%</width></action>

    </keybind>

    <keybind key="C-W-Right">        # HalfRightScreen

      <action name="UnmaximizeFull"/>

      <action name="MoveResizeTo"><x>-0</x><y>0</y><height>100%</height><width>50%</width></action>

    </keybind>



    <keybind key="C-W-1">        # UpperQuarterLeft

      <action name="UnmaximizeFull"/>

      <action name="MoveResizeTo"><x>0</x><y>0</y><height>50%</height><width>50%</width></action>

    </keybind>



    <keybind key="C-W-2">        # LowerQuarterLeft

      <action name="UnmaximizeFull"/>

      <action name="MoveResizeTo"><x>0</x><y>-0</y><height>50%</height><width>50%</width></action>

    </keybind>



    <keybind key="C-W-3">        # LowerQuarterRight

      <action name="UnmaximizeFull"/>

      <action name="MoveResizeTo"><x>-0</x><y>-0</y><height>50%</height><width>50%</width></action>

    </keybind>



    <keybind key="C-W-4">        # UpperQuarterRight

      <action name="UnmaximizeFull"/>

      <action name="MoveResizeTo"><x>-0</x><y>0</y><height>50%</height><width>50%</width></action>

    </keybind>

You might have to tweak the percentages based on whether you use a panel or not.

C-W-Up means CTRL + SUPER + ↑