For large balena fleets, it may be necessary to run this from the Chrome dev console.

delete-device-config-var-overrides.js

// This script may be run in a Chrome dev console, and will delete all the device config variables for each device in a fleet,
// which the exception of *_SUPERVISOR_DELTA or *_SUPERVISOR_DELTA_VERSION.
await (async () => {
    // Make sure FLEET_ID is the ID of your fleet.
    const FLEET_ID = 12345;
    
    // Get devices in fleet
    const devices = await sdk.models.device.getAllByApplication(FLEET_ID, {
        $select: 'id',
    });
    const deviceIds = devices.map(d => d.id);
  
    console.log('NUMBER OF DEVICES:', devices.length);
    
    for (const id of deviceIds) {
        const configs = (await sdk.models.device.configVar.getAllByDevice(id)).filter(vars => !vars.name.includes('SUPERVISOR_DELTA'));
        for (const config of configs) {
            await sdk.models.device.configVar.remove(id, config.name);
        }
    }
    
    console.log('Done removing device config var overrides');
})();