There are no plans to update Galaxy Watch Studio. I believe the team was disbanded 3 years ago.
The only way to create a Distributor Certificate for Tizen Devices is using Tizen Studio certificate manager tool. I think you can install using Tizen Studio or SDB command lines but I haven’t had time to check that out for proof.
You can use the Fit2Installerfor now.
@tacokoneko instructions are pretty complete but with the updated Certificate extension it asks you to launch your default browser to get the certificates.
Ron
Samsung Developer Relations