your code should be between [CODE]...[/CODE] tags like
Code:
let
Source = Excel.CurrentWorkbook(){[Name="Table1"]}[Content],
#"Changed Type" = Table.TransformColumnTypes(Source,{{"IDoc number", Int64.Type}, {"Counter", Int64.Type}, {"Segment No.", Int64.Type}, {"SAP segment name", type text}, {"No. higher segment", Int64.Type}, {"Hierarchy level", Int64.Type}, {"Data Filter Value fo", type any}, {"Length", Int64.Type}, {"Application data", type text}}),
#"Removed Columns" = Table.RemoveColumns(#"Changed Type",{"Data Filter Value fo", "Hierarchy level", "No. higher segment", "Counter"}), AddedIndex = Table.AddIndexColumn(#"Removed Columns", "Index", 0, 1),
#"Added Custom1" = Table.AddColumn(AddedIndex, "PO Number", each if [#"Segment No."] = 1 then Text.Trim (Text.Start([Application data],35)) else {[Index]-1}[#"PO Number"])
in
#"Added Custom1"
and post example data associated with this code
[TABLE="width: 784"]
<colgroup><col width="105" style="width: 79pt; mso-width-source: userset; mso-width-alt: 3840;"> <col width="150" style="width: 113pt; mso-width-source: userset; mso-width-alt: 5485;"> <col width="67" style="width: 50pt; mso-width-source: userset; mso-width-alt: 2450;"> <col width="568" style="width: 426pt; mso-width-source: userset; mso-width-alt: 20772;"> <col width="59" style="width: 44pt; mso-width-source: userset; mso-width-alt: 2157;"> <col width="96" style="width: 72pt; mso-width-source: userset; mso-width-alt: 3510;"> <tbody>[TR]
[TD="width: 105"]Segment No.[/TD]
[TD="width: 150"]SAP segment name[/TD]
[TD="width: 67"]Length[/TD]
[TD="width: 568"]Application data[/TD]
[TD="width: 59"]Index[/TD]
[TD="width: 96"]PO Number[/TD]
[/TR]
[TR]
[TD="align: right"]1[/TD]
[TD]E1EDK09[/TD]
[TD="align: right"]1000[/TD]
[TD]A11517 20190625190625 B[/TD]
[TD="align: right"]-1[/TD]
[TD]A11517[/TD]
[/TR]
[TR]
[TD="bgcolor: transparent, align: right"]2[/TD]
[TD="bgcolor: transparent"]E1EDKA1[/TD]
[TD="bgcolor: transparent, align: right"]1000[/TD]
[TD="bgcolor: transparent"]LF FTL MFG[/TD]
[TD="bgcolor: transparent, align: right"]0[/TD]
[TD="bgcolor: transparent"] [/TD]
[/TR]
[TR]
[TD="align: right"]3[/TD]
[TD]E1EDKA1[/TD]
[TD="align: right"]1000[/TD]
[TD]YSCBW 7[/TD]
[TD="align: right"]1[/TD]
[TD] [/TD]
[/TR]
[TR]
[TD="bgcolor: transparent, align: right"]4[/TD]
[TD="bgcolor: transparent"]E1EDK11[/TD]
[TD="bgcolor: transparent, align: right"]1000[/TD]
[TD="bgcolor: transparent"]YHT1 1 Customer Horizon Start Date: 06/25/19 Customer Horizon End Date: 12/22/19[/TD]
[TD="bgcolor: transparent, align: right"]2[/TD]
[TD="bgcolor: transparent"] [/TD]
[/TR]
[TR]
[TD="align: right"]5[/TD]
[TD]E1EDK11[/TD]
[TD="align: right"]1000[/TD]
[TD]YHT1 2 TMP 92 = 001[/TD]
[TD="align: right"]3[/TD]
[TD] [/TD]
[/TR]
[TR]
[TD="bgcolor: transparent, align: right"]6[/TD]
[TD="bgcolor: transparent"]E1EDP10[/TD]
[TD="bgcolor: transparent, align: right"]1000[/TD]
[TD="bgcolor: transparent"]BW K151860 001 0.000000 20190624 20190625 0.000000 03 534[/TD]
[TD="bgcolor: transparent, align: right"]4[/TD]
[TD="bgcolor: transparent"] [/TD]
[/TR]
[TR]
[TD="align: right"]7[/TD]
[TD]E1EDP16[/TD]
[TD="align: right"]1000[/TD]
[TD]4W20190809 20190809 6[/TD]
[TD="align: right"]5[/TD]
[TD] [/TD]
[/TR]
[TR]
[TD="bgcolor: transparent, align: right"]1[/TD]
[TD="bgcolor: transparent"]E1EDK09[/TD]
[TD="bgcolor: transparent, align: right"]1000[/TD]
[TD="bgcolor: transparent"]A11517 20190625190625 B[/TD]
[TD="bgcolor: transparent, align: right"]6[/TD]
[TD="bgcolor: transparent"]A11517[/TD]
[/TR]
</tbody>[/TABLE]