TL;DR
Newer versions of resources for google_compute_network, google_compute_subnetwork, routes, etc have the capabilities to attach resource manager tags in their params block. This does not seem to be supported yet
Terraform Resources
https://registry.terraform.io/providers/hashicorp/google/latest/docs/resources/compute_network#params-1
https://registry.terraform.io/providers/hashicorp/google/latest/docs/resources/compute_subnetwork#params-1
https://registry.terraform.io/providers/hashicorp/google/latest/docs/resources/compute_route#params-2
Detailed design
Additional information
No response