Swap from default to 'core' to be consistent with the namespace of the file.

config/plugins/tours/core.galaxy_ui.yaml

@@ -3,7 +3,7 @@ name: Galaxy UI
 description: A gentle introduction to the Galaxy User Interface
 title_default: "Welcome to Galaxy"
 tags:
-  - "default"
+  - "core"
   - "UI"
 
 # A tour is made of several steps, each of them beginning with a dash '-'

config/plugins/tours/core.history.yaml

@@ -2,7 +2,7 @@ name: History Introduction
 description: A detailed introduction to the Galaxy History
 title_default: "Galaxy History Introduction"
 tags:
-  - "default"
+  - "core"
   - "history"
 
 steps:

config/plugins/tours/core.scratchbook.yaml

@@ -2,7 +2,7 @@ name: Scratchbook - Introduction
 title_default: "Scratchbook Introduction"
 description: "An introduction on how to display multiple datasets and visualizations next to each other."
 tags:
-  - "default"
+  - "core"
   - "UI"
   - "visualization"