You have a requirement to nullify (empty/remove) a value entered in a field in Materials. But this is not possible using Mass Change functionality.
SAP Business ByDesign
It is not possible to nullify a value of parameter in Material Master Data using Mass Change or Migration or through Mass Data Maintenance functionalities.
Basically, using Mass Change of Materials, Mass Data Maintenance or using Migration, you can modify an existing value or add a new value to the parameter, but it is not possible to nullify values due to technical constrains.
KBA , nullify , AP-RC-BCT , Business Config. Tools (SAP Business ByDesign , How To