Answer by Michael Olafisoye for how to implement "sticky" variables in terraform?

This document says nothing about maintaining state which is what you need but it does have useful info on variables - https://medium.com/@milescollier/handling-environmental-variables-in-terraform-workspaces-27d0278423df

you can also do -

variable "template" {
    type = "string"
    default = "01000000-0000-4000-8000-000030080200"
}

or 

variable "environment-type" {
  type = "map"

  default = {
    dev = "DEVELOPMENT"
    preprod = "PRE-PRODUCTION"
    prod = "PRODUCTION"
  }
}