if you open the Client and there the HELP you will find "Specifying merge settings" which should give a clean overview about how it works.
Replace: All content in the master catalog is overwritten; content in the master catalog is also deleted if it is not included in the supplier catalog.
About empty values there is also a setting in plugin_customzation.ini which can have an effect.
thank you for your answer.
Do you mean it is not possible to specify the merge configuration if I choose "replacement", although the selection is given?
But in case, if you want to remove 5 old pics of typ "application image" in master catalog and put 3 new pics from the supplier catalog, there is no possibilty for this use case through merge process. Are you with me?
You can give a try using "Overwrite" option rather than "Replace" in your merge settings.
At subentity level, Replace and Overwrite has minor difference.
For example I have two attributes in Master catalog(color and Size).
in Supplier catalog I have only one attribute with name Color.
Now with replace at ArticleAttribute Level, it will do changes for Color attribute in master catalog as per Supplier catalog and will also delete the Size attribute from Master catalog since attribute with Size name is not there in Supplier catalog.
However with overwrite merge setting, it will merge the color attribute changes from Supplier catalog in master catalog but will not delete the Color attribute from master catalog