That an interesting one. The only mention of GameplayDebuggingComponent over 5.3 engine code i found is Engine\Plugins\NetcodeUnitTest\NUTUnrealEngine\Source\NUTUnrealEngine\Classes\UnitTests\Obsolete\UTT61_DebugReplicateData.h, which is obviously obsolete.
So i guess it’s a doc for a feature that was scrapped, but the doc itself makes it to the present, and even got marked as “5.5”. Features are rarely got scrapped without providing any alternative, but unfortunately i’m not aware about its current name.