it should get the TOC from the global _toc.yaml...

_toc.yml

@@ -4,10 +4,8 @@
 root: index
 format: jb-book
 
-parts:
-  - caption: User Guide
-    chapters:
-      - file: user-guide/index
+  chapters:
+    - file: user-guide/index
         sections:
           - file: user-guide/login_servers
           - file: user-guide/evolution_for_o365
@@ -18,9 +16,6 @@ parts:
           - file: user-guide/kerberos_lifetime
           - file: user-guide/putty
 
-  - caption: Admin Guide
-    maxdepth: 2
-    chapters:
     - file: admin-guide/index
       sections:
         - file: admin-guide/architecture
@@ -47,26 +42,24 @@ parts:
         - file: admin-guide/troubleshooting
         - file: admin-guide/more
 
-  - caption: Infrastructure Guide
-    chapters:
-      - file: infrastructure-guide/infrastructure_systems
-        sections:
-          - file: infrastructure-guide/boot_server
-          - file: infrastructure-guide/sysdb_server
-          - file: infrastructure-guide/puppet01
-          - file: infrastructure-guide/repo_server
-          - file: infrastructure-guide/lxweb00
-          - file: infrastructure-guide/login
-          - file: infrastructure-guide/influx00
-          - file: infrastructure-guide/metrics00
-          - file: infrastructure-guide/lxsup00
-      - file: infrastructure-guide/infrastructure_administration
-      - file: infrastructure-guide/troubleshooting
+    - file: infrastructure-guide/index
+      sections:
+        - file: infrastructure-guide/infrastructure_systems
+          sections:
+            - file: infrastructure-guide/boot_server
+            - file: infrastructure-guide/sysdb_server
+            - file: infrastructure-guide/puppet01
+            - file: infrastructure-guide/repo_server
+            - file: infrastructure-guide/lxweb00
+            - file: infrastructure-guide/login
+            - file: infrastructure-guide/influx00
+            - file: infrastructure-guide/metrics00
+            - file: infrastructure-guide/lxsup00
+        - file: infrastructure-guide/infrastructure_administration
+        - file: infrastructure-guide/troubleshooting
 
-  - caption: RHEL8
-    chapters:
-      - file: rhel8/index
-        sections:
+    - file: rhel8/index
+      sections:
           - file: rhel8/installation
           - file: rhel8/software
           - file: rhel8/nvidia