In the SAP function module world, this is usually done using:
👉 REUSE_ALV_HIERSEQ_LIST_DISPLAY

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*& Report  ZTEST_PROGRAM_2
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REPORT ztest_program_2.

TYPE-POOLS: slis.

DATA: it_mara TYPE TABLE OF mara,
it_marc TYPE TABLE OF marc.

DATA: it_fieldcat_header TYPE slis_t_fieldcat_alv,
it_fieldcat_item   TYPE slis_t_fieldcat_alv,
wa_fieldcat        TYPE slis_fieldcat_alv.

DATA: gs_keyinfo TYPE slis_keyinfo_alv.

“— Fetch Data (limit for demo)
SELECT * FROM mara UP TO 10 ROWS INTO TABLE it_mara.
SELECT * FROM marc UP TO 50 ROWS INTO TABLE it_marc.

“— Build Field Catalog for MARA (Header)
CLEAR wa_fieldcat.
wa_fieldcat–fieldname = ‘MATNR’.
wa_fieldcat–seltext_m = ‘Material’.
APPEND wa_fieldcat TO it_fieldcat_header.

CLEAR wa_fieldcat.
wa_fieldcat–fieldname = ‘MTART’.
wa_fieldcat–seltext_m = ‘Material Type’.
APPEND wa_fieldcat TO it_fieldcat_header.

“— Build Field Catalog for MARC (Item)
CLEAR wa_fieldcat.
wa_fieldcat–fieldname = ‘MATNR’.
wa_fieldcat–seltext_m = ‘Material’.
APPEND wa_fieldcat TO it_fieldcat_item.

CLEAR wa_fieldcat.
wa_fieldcat–fieldname = ‘WERKS’.
wa_fieldcat–seltext_m = ‘Plant’.
APPEND wa_fieldcat TO it_fieldcat_item.

CLEAR wa_fieldcat.
wa_fieldcat–fieldname = ‘DISMM’.
wa_fieldcat–seltext_m = ‘MRP Type’.
APPEND wa_fieldcat TO it_fieldcat_item.

“— Key Information (join condition between header and item)
gs_keyinfo–header01 = ‘MATNR’. ” Header Key
gs_keyinfo–item01   = ‘MATNR’. ” Item Key

“— Display Hierarchical ALV
CALL FUNCTION ‘REUSE_ALV_HIERSEQ_LIST_DISPLAY’
EXPORTING
i_callback_program      = sy–repid
is_keyinfo              = gs_keyinfo
i_structure_name_header = ‘MARA’
i_structure_name_item   = ‘MARC’
i_tabname_header        = ‘MARA’
i_tabname_item          = ‘MARC’
TABLES
t_outtab_header         = it_mara
t_outtab_item           = it_marc
EXCEPTIONS
program_error           = 1
OTHERS                  = 2.

IF sy–subrc <> 0.
MESSAGE ID sy–msgid TYPE sy–msgty NUMBER sy–msgno
WITH sy–msgv1 sy–msgv2 sy–msgv3 sy–msgv4.
ENDIF.

Output: