When you introduce a new singleton, the following is suggested as a data migration:

  <add-annotations name="my.module">
    <annotations>
      <singletons>
        <singleton name="MY_OBJECT"
          type="MyObject"
        />
      </singletons>
    </annotations>
  </add-annotations>
  <create-singleton name="MY_OBJECT"
    module="my.module"
  >
    <singleton
      table="GenericObject"
      type="my.module:MyObject"
    />
  </create-singleton>

However, when you run these, the application fails to start and throws the following exception:

java.lang.RuntimeException: com.top_logic.basic.module.ModuleException: Unable to start implementation 'com.top_logic.element.model.DynamicModelService@7aa32b52'.
	at com.top_logic.util.AbstractStartStopListener.contextInitialized(AbstractStartStopListener.java:245)
    at ...
Caused by: com.top_logic.basic.module.ModuleException: Unable to start implementation 'com.top_logic.element.model.DynamicModelService@7aa32b52'.
    at com.top_logic.basic.module.BasicRuntimeModule.startUpImplementation(BasicRuntimeModule.java:199)
	at com.top_logic.basic.module.BasicRuntimeModule.startUp(BasicRuntimeModule.java:179)
    at com.top_logic.basic.module.BasicRuntimeModule.startUp(BasicRuntimeModule.java:152)
	at com.top_logic.basic.module.ModuleUtil.start(ModuleUtil.java:263)
    at com.top_logic.basic.module.ModuleUtil.startModuleAndAdd(ModuleUtil.java:768)
	at com.top_logic.basic.module.ModuleUtil$3.run(ModuleUtil.java:744)
    at com.top_logic.basic.module.ModuleUtil$3.run(ModuleUtil.java:1)
	at com.top_logic.basic.thread.ThreadContextManager.inInteractionInternal(ThreadContextManager.java:404)
    at com.top_logic.basic.thread.ThreadContextManager.inSystemInteractionInternal(ThreadContextManager.java:446)
	at com.top_logic.basic.thread.ThreadContextManager.inSystemInteraction(ThreadContextManager.java:438)
    at com.top_logic.basic.module.ModuleUtil.startInThreadContext(ModuleUtil.java:753)
	at com.top_logic.basic.module.ModuleUtil.startModulesAndAdd(ModuleUtil.java:717)
    at com.top_logic.basic.module.ModuleUtil.startUp(ModuleUtil.java:243)
	at com.top_logic.util.AbstractStartStopListener.startTokenSystem(AbstractStartStopListener.java:552)
    at com.top_logic.util.AbstractStartStopListener$2.run(AbstractStartStopListener.java:260)
	at com.top_logic.util.AbstractStartStopListener$2.run(AbstractStartStopListener.java:1)
    at com.top_logic.basic.thread.ThreadContextManager.inInteractionInternal(ThreadContextManager.java:385)
	at com.top_logic.basic.thread.ThreadContextManager.inSystemInteractionInternal(ThreadContextManager.java:446)
    at com.top_logic.basic.thread.ThreadContextManager.inSystemInteraction(ThreadContextManager.java:438)
	at com.top_logic.basic.thread.ThreadContext.inSystemContext(ThreadContext.java:157)
    at com.top_logic.util.AbstractStartStopListener.boot(AbstractStartStopListener.java:252)
	at com.top_logic.util.AbstractStartStopListener.contextInitialized(AbstractStartStopListener.java:206)
    ... 24 more
Caused by: java.lang.IllegalStateException: Cannot parse old model configuration; schema upgrade not possible.
	at com.top_logic.element.model.DynamicModelService.upgradeModel(DynamicModelService.java:422)
    at com.top_logic.element.model.DynamicModelService.setupModel(DynamicModelService.java:345)
	at com.top_logic.element.model.DynamicModelService.startUpInContext(DynamicModelService.java:320)
    at com.top_logic.util.model.ModelService$1.inContext(ModelService.java:224)
	at com.top_logic.basic.thread.ThreadContextManager.inInteractionInternal(ThreadContextManager.java:322)
    at com.top_logic.basic.thread.ThreadContextManager.inSystemInteractionInternal(ThreadContextManager.java:348)
	at com.top_logic.basic.thread.ThreadContextManager.inSystemInteraction(ThreadContextManager.java:341)
    at com.top_logic.basic.thread.ThreadContext.inSystemContext(ThreadContext.java:176)
	at com.top_logic.util.model.ModelService.startUp(ModelService.java:220)
    at com.top_logic.basic.module.ManagedClass.doStart(ManagedClass.java:123)
	at com.top_logic.basic.module.BasicRuntimeModule.startUpImplementation(BasicRuntimeModule.java:197)
    ... 45 more
Caused by: com.top_logic.basic.config.ConfigurationException: "Errors in context: Invalid indexed property entry for property 'name' (com.top_logic.element.config.SingletonConfig.getName()) at [no name] line 71 column 3695: Multiple entries with key: MY_OBJECT"
	at com.top_logic.basic.config.InstantiationContextImpl.toConfigurationException(InstantiationContextImpl.java:94)
    at com.top_logic.basic.config.InstantiationContextImpl.checkErrors(InstantiationContextImpl.java:54)
	at com.top_logic.basic.config.InstantiationContextAdaptor.checkErrors(InstantiationContextAdaptor.java:60)
    at com.top_logic.basic.config.AbstractConfigurationReader.checkSuccess(AbstractConfigurationReader.java:237)
	at com.top_logic.basic.config.AbstractConfigurationReader.read(AbstractConfigurationReader.java:228)
    at com.top_logic.basic.config.AbstractConfigurationReader.read(AbstractConfigurationReader.java:194)
	at com.top_logic.basic.config.TypedConfiguration.readConfig(TypedConfiguration.java:732)
    at com.top_logic.basic.config.TypedConfiguration.parse(TypedConfiguration.java:688)
	at com.top_logic.basic.config.TypedConfiguration.parse(TypedConfiguration.java:664)
    at com.top_logic.element.model.DynamicModelService.parseConfig(DynamicModelService.java:491)
    at com.top_logic.element.model.DynamicModelService.loadTransientModel(DynamicModelService.java:481)
    at com.top_logic.element.model.DynamicModelService.upgradeModel(DynamicModelService.java:420)
    ... 55 more

In other words, the migration creates the annotation for the singleton twice. Specifically, the class com.top_logic.element.model.migration.model.CreateTLSingletonProcessor calls MigrationUtils.modifyTLModel(log, connection, tlModel -> addSingletonDefinition(log, tlModel)); on line 152, which it presumably should not be doing.