Here are the missing parts that you asked for:
The other Log Message activities, where the error occurs and at the bottom the tried adding of the Name and Value columns into a Dictionary<String,Object>. Moreover, the third column Description that is not used for loading into the dictionary but as a description/annotation.
Log Message activities excerpt of InitAllSettings.xaml workflow:
Config.xlsx, where the column “Value” cannot be loaded:
The InitAllSettings.xaml file that was making the troubles:
InitAllSettings.xaml (37.4 KB)
I thank you for your support and answers!