You need to edit the options.xml file:
https://www.radiantviewer.com/dicom-viewer-manual/options_xml.htm
Specifically this section:
<window>
<presets> <!-- window settings - presets -->
<!-- <i m="CT" i="8" n="Preset 1" ww="70" wl="30"/> --> <!-- m - modality (CR, CT, MR, XA, MG, etc.), i - shortcut key (2-9), n - preset name, ww - window width, wl - window level -->
<!-- <i m="CT" i="9" n="Preset 2" ww="32" wl="30"/> -->
</presets>
</window>