You might want to make Main Company and Subsidiaries different occurrences of the same table.
It's actually quite easy to list all key processes. Any layout based on KeyProcesses will list all records in that data source table, but the challenge will be showing data from the correct parent table: Main Company and Subsidiaries--which is where making Subsidiaries an occurrence of Main Company makes this part easier.
MainCompany::CompanyID = Subsidiaries::MainCompanyID
MainCompany::CompanyID = MainKeyProcesses::CompanyID
Subsidiaries::CompanyID = SubKeyProcesses::CompanyID