Although I do not indicate the model of your Smartwatch I will give the 2 options:
For models with the Play Store that does not have the possibility of establishing a third-party Widget, a good option is to use “Universal Launcher New Gen” developed by @Eric_Crochemore:
The thread in the forum is this:
In the devices that I have tried it works, but it changes the luncher of your smartwatch.
If your Smartwatch is an Amazfit the latest version of the Widget is 10.2 if it works with versions 10 and 11 of Watch Droid