A Karabiner config to mimic the half-handed QWERTY behavior and layout of the Matias one-handed keyboards.

matias-like one-handed qwerty for karabiner.xml

<root>
<item>
<!-- a brief discussion about this config was originally posted here https://groups.google.com/d/topic/osx-karabiner/4TdHyfImc-k I lifted it and changed the Name -->

<name>Matias Style One-handed Half-QWERTY</name>
<identifier>Half-QWERTY</identifier>
<autogen>
__HoldingKeyToKey__, KeyCode::SPACE, KeyCode::SPACE, KeyCode::VK_NONE, KeyCode::VK_CONFIG_SYNC_KEYDOWNUP_notsave_flip_hands
</autogen>
</item>
<item hidden="true">
<identifier vk_config="true">notsave.flip_hands</identifier>
<autogen>__ShowStatusMessage__ Flip hands</autogen>
<!--  Left hand  -->
<!--  Top row  -->
<autogen>__KeyToKey__, KeyCode::KEY_1, KeyCode::KEY_0</autogen>
<autogen>__KeyToKey__, KeyCode::KEY_2, KeyCode::KEY_9</autogen>
<autogen>__KeyToKey__, KeyCode::KEY_3, KeyCode::KEY_8</autogen>
<autogen>__KeyToKey__, KeyCode::KEY_4, KeyCode::KEY_7</autogen>
<autogen>__KeyToKey__, KeyCode::KEY_5, KeyCode::KEY_6</autogen>
<!--  Upper row  -->
<autogen>__KeyToKey__, KeyCode::Q, KeyCode::P</autogen>
<autogen>__KeyToKey__, KeyCode::W, KeyCode::O</autogen>
<autogen>__KeyToKey__, KeyCode::E, KeyCode::I</autogen>
<autogen>__KeyToKey__, KeyCode::R, KeyCode::U</autogen>
<autogen>__KeyToKey__, KeyCode::T, KeyCode::Y</autogen>
<!--  Home row  -->
<autogen>__KeyToKey__, KeyCode::A, KeyCode::SEMICOLON</autogen>
<autogen>__KeyToKey__, KeyCode::S, KeyCode::L</autogen>
<autogen>__KeyToKey__, KeyCode::D, KeyCode::K</autogen>
<autogen>__KeyToKey__, KeyCode::F, KeyCode::J</autogen>
<autogen>__KeyToKey__, KeyCode::G, KeyCode::H</autogen>
<!--  Lower row  -->
<autogen>__KeyToKey__, KeyCode::Z, KeyCode::SLASH</autogen>
<autogen>__KeyToKey__, KeyCode::X, KeyCode::DOT</autogen>
<autogen>__KeyToKey__, KeyCode::C, KeyCode::COMMA</autogen>
<autogen>__KeyToKey__, KeyCode::V, KeyCode::M</autogen>
<autogen>__KeyToKey__, KeyCode::B, KeyCode::N</autogen>
<!--  Right hand  -->
<!--  Top row  -->
<autogen>__KeyToKey__, KeyCode::KEY_6, KeyCode::KEY_5</autogen>
<autogen>__KeyToKey__, KeyCode::KEY_7, KeyCode::KEY_4</autogen>
<autogen>__KeyToKey__, KeyCode::KEY_8, KeyCode::KEY_3</autogen>
<autogen>__KeyToKey__, KeyCode::KEY_9, KeyCode::KEY_2</autogen>
<autogen>__KeyToKey__, KeyCode::KEY_0, KeyCode::KEY_1</autogen>
<!--  Upper row  -->
<autogen>__KeyToKey__, KeyCode::Y, KeyCode::T</autogen>
<autogen>__KeyToKey__, KeyCode::U, KeyCode::R</autogen>
<autogen>__KeyToKey__, KeyCode::I, KeyCode::E</autogen>
<autogen>__KeyToKey__, KeyCode::O, KeyCode::W</autogen>
<autogen>__KeyToKey__, KeyCode::P, KeyCode::Q</autogen>
<!--  Home row  -->
<autogen>__KeyToKey__, KeyCode::H, KeyCode::G</autogen>
<autogen>__KeyToKey__, KeyCode::J, KeyCode::F</autogen>
<autogen>__KeyToKey__, KeyCode::K, KeyCode::D</autogen>
<autogen>__KeyToKey__, KeyCode::L, KeyCode::S</autogen>
<autogen>__KeyToKey__, KeyCode::SEMICOLON, KeyCode::A</autogen>
<!--  Lower row  -->
<autogen>__KeyToKey__, KeyCode::N, KeyCode::B</autogen>
<autogen>__KeyToKey__, KeyCode::M, KeyCode::V</autogen>
<autogen>__KeyToKey__, KeyCode::COMMA, KeyCode::C</autogen>
<autogen>__KeyToKey__, KeyCode::DOT, KeyCode::X</autogen>
<autogen>__KeyToKey__, KeyCode::SLASH, KeyCode::Z</autogen>
</item>
</root>