Comment 2 for bug 1393357

The Properties Action is set here:
https://github.com/mixxxdj/mixxx/blob/42c61e010cfd93f9bbc304cf9fb348ec4d315743/src/widget/wtracktableview.cpp#L393

    m_pPropertiesAct->setShortcut(
        QKeySequence(m_pKbdConfig->getValueString(ConfigKey("[KeyboardShortcuts]", ... ), tr("Ctrl+i"))));

IMHO this should show the short cut in the menu.