Can you edit AMDP class in the SAP GUI?

No. You can’t edit ABAP Managed Database Procedures (AMDP) class in the SAP GUI. If you try to edit an AMDP class called ZCL_DEMO in SAP GUI using SE24 transaction code, you will get an error "Class ZCL_DEMO contains stored procedures which cannot be changed in SAP GUI".

Since you can’t edit AMDP class in SAP GUI you need to use ABAP Development Tools (Eclipse or HANA Studio).