If you pair your electric blanket with either the Tuya or SmartLife app instead of the Sunbeam app the scene (tap and run) work around should give you partial 1 way control in ST.
You would need to create a scene in Tuya for each temperature level you want, and would also need 1 for off.
Smartthings can send on/off commands to Tuya, but Tuya sends nothing back to Smartthings.
Electric blankets are listed under small home appliances in both the Tuya and SmartLife apps.
I use this workaround for many things including a Honeywell dehumidifier. Instead of using the Honeywell app I paired it with the SmartLife app. Then I have ST routines that incorporate humidity sensors, door contacts, temperature sensors, and thermostat modes.