This article explains how to customize DRV binding keys with $HOME/.calibrewb_workspace/keyprefs file.
Details
DRV default binding keys can be modified/changed with the keyprefs file. The file contains the definitions for the key and mouse wheel bindings and is automatically loaded when you invoke a layout viewer.
The keyprefs template file is available through the following symbolic link: $HOME/.calibrewb_workspace/keyprefs.template
When the user invokes the layout viewer, it automatically creates a link in the $HOME/.calibrewb_workspace directory to a template keyprefs file in the $CALIBRE_HOME directory.
There is no mechanism in the layout viewer GUI to modify a keyprefs file, but users can create a custom keyprefs file by creating it in $HOME/.calibrewb_workspace directory.
At invocation, if the $HOME/.calibrewb_workspace/keyprefs file exists, the layout viewer will automatically load it. Otherwise, the layout viewer uses the default key bindings.