Solution : https://service.sap.com/sap/support/notes/567717 (SAP Service marketplace login required)
Key words :
key guid = lv_guid product = lv_product assignment_guid = lv_asgn_guid assigning <ls_item_copy_ui>, product selection tab page, 'activity plan' tab page, double-click event opport_hd_act, sv_header_guid type crmt_object_guid, sv_process_type type crmt_process_type, sv_object_type type swo_objtyp, ss_proc_type type crmc_proc_type, =======================================================================class cl_crm_bsp_intlay_1omethod check_followup_button, read table gt_item_copy_ui