Learning loads about YAML and now it's working - sort of.

db/migrate/20230127131552_add_condition_to_sub_principal_item_groups.rb

@@ -0,0 +1,5 @@
+class AddConditionToSubPrincipalItemGroups < ActiveRecord::Migration[7.0]
+  def change
+    add_column :subprincipleitemgroups, :condition, :string
+  end
+end

db/schema.rb

@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema[7.0].define(version: 2023_01_27_095856) do
+ActiveRecord::Schema[7.0].define(version: 2023_01_27_131552) do
   create_table "action_text_rich_texts", charset: "utf8mb4", force: :cascade do |t|
     t.string "name", null: false
     t.text "body", size: :long
@@ -95,6 +95,7 @@ ActiveRecord::Schema[7.0].define(version: 2023_01_27_095856) do
     t.string "type"
     t.datetime "created_at", null: false
     t.datetime "updated_at", null: false
+    t.string "condition"
     t.index ["subprinciple_id"], name: "index_subprincipleitemgroups_on_subprinciple_id"
   end