Hi,
Declare lv_ venqty as string, then do the following, highlighted in green.
CONCATENATEw_donum w_matnr w_sdate w_stime w_ddate w_dtime w_lifnr w_venqty w_reqqty w_cur_deliv
w_cur_reqqty w_zzpszdo w_arbpl w_model w_werks w_lgort w_aufnr w_auart w_meins w_mfgline w_shift w_plndt
INTOlw_cont_txt SEPARATEDBY
cl_abap_char_utilities=>horizontal_tab.
CONCATENATEcl_abap_char_utilities=>cr_lf lw_cont_txt INTOlw_cont_txt.
APPENDlw_cont_txt.
CLEARlw_cont_txt.
LOOPATgt_step03.
MOVE gt_step03-venqty to lv_ venqty.
CONCATENATEgt_step03-donum gt_step03-matnr gt_step03-sdate gt_step03-stime gt_step03-ddate gt_step03-dtime
gt_step03-lifnr lv_ venqtygt_step03-reqqty gt_step03-cur_deliv gt_step03-cur_reqqty gt_step03-zzpszdo
gt_step03-arbpl gt_step03-model
gt_step03-werks gt_step03-lgort gt_step03-aufnr gt_step03-auart gt_step03-meins
gt_step03-mfgline gt_step03-shiftgt_step03-plndt
INTOlw_cont_txt SEPARATEDBY
cl_abap_char_utilities=>horizontal_tab.
CONCATENATEcl_abap_char_utilities=>cr_lf lw_cont_txt INTO
lw_cont_txt.
APPENDlw_cont_txt.