Hi! Thank you for your comments. You can set the default tools in the options.xml file:
https://www.radiantviewer.com/dicom-viewer-manual/options_xml.htm
<tools> <!-- tools assigned to mouse buttons (1 - browse series, 2 - zoom, 3 - pan, 4 - change WW/WL, 5 - ROI) -->
<lmb>1</lmb> <!-- left mouse button -->
<mmb>4</mmb> <!-- middle mouse button -->
<rmb>2</rmb> <!-- right mouse button -->
<mw>1</mw> <!-- mouse wheel - valid tools: browse series (1) or zoom (2) -->
</tools>