A comment explains the link anchor.

doc/versioning/submod_versioning.md

@@ -545,7 +545,7 @@ If new entries appear in .gitmodules with the pull, they will not be processed a
 the sequence of pull and "submodule update".
 
 
-(changing-a-submodule-branch)=
+(Changing a Submodule Branch)= <!-- !!! keep this link anchor, because referenced later !!! -->
 #### Changing a Submodule Branch
 
 This scenario describes the change of a submodule to another existing
@@ -903,6 +903,7 @@ To use the new version in the base repository, use the commands
 from [Changing a Submodule Branch](#changing-a-submodule-branch) and use
 the new branch name there.
 
+
 #### Creating a New System Version
 
 Creating a complete system version starts by creating a new version for