Unity versions 2020.3 - 2021 have an editor bug that draws lists incorrectly in the inspector. It's already been reported to Unity.
You may see it when editing Custom Lua Function Info assets or your own scripts that include nested lists:
A temporary workaround for CustomLuaFunctionInfo is to edit Assets / Plugins / Pixel Crushers / Dialogue System / Scripts / Utility / CustomLuaFunctionInfo.cs. Swap the order of these two lines: