In QElectroTech: File → New → Element . Set a meaningful name: Siemens_S7-1500_DQ_16x24VDC_BA .
Because this is user-community driven, the symbols are fully editable. If a specific Siemens variant isn't present, the existing symbols serve as an excellent template for modification. This is a significant advantage over rigid, proprietary libraries found in paid software. qelectrotech siemens library