Define an input variable e.g. addTagToRG_policy_id_0 for each policy definition resource created by the policy definition resource block that uses count.

AzurePolicyInputVariable.tf

variable "addTagToRG_policy_id_0" {
  type        = string
  description = "The policy definition id '0' from the 'addTagToRG_policy_ids' output"
}

variable "addTagToRG_policy_id_1" {
  type        = string
  description = "The policy definition id '1' from the 'addTagToRG_policy_ids' output"
}

variable "addTagToRG_policy_id_2" {
  type        = string
  description = "The policy definition id '2' from the 'addTagToRG_policy_ids' output"
}

variable "addTagToRG_policy_id_3" {
  type        = string
  description = "The policy definition id '3' from the 'addTagToRG_policy_ids' output"
}

variable "addTagToRG_policy_id_4" {
  type        = string
  description = "The policy definition id '4' from the 'addTagToRG_policy_ids' output"
}

variable "addTagToRG_policy_id_5" {
  type        = string
  description = "The policy definition id '5' from the 'addTagToRG_policy_ids' output"
}