Read environment variable from other environment

GitLab CI/CD
1

Hi

I wanted to know, how we can read a variable from another environment.

Essentially I am keeping container image in different container repositories each for sit, uat and prod environment in cloud and maps these cloud environment to gitlab environments for configurations.

Lets say now
sit env have environment variable as APP1_REGISTRY and its value as https://sit-registry
uat env have environment variable as APP1_REGISTRY and its value as https://uat-registry

Now I want to access sit env APP1_REGISTERY in uat env to pull, retag and push to uat registry. How to achieve it?

Thanks