Combine text on condition

Hello kulkarni21vinee - 

Below is an example of how you can achieve your desired output. Note, in your description you mention that if Maintenance Task starts with OPEN-O then then delimiter should be a line feed/line break/carriage return.  However, the expected output posted does not actually show the extra line.  Please have a look at this solution and if it does not meet your needs, please provide some additional information so I can revise the solution to something suitable.

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("bY5BDsIgFESvMmFdE/QGtR0KCfARPpqm6f2v0brQuHA97+XNthlr7dUMZpKsY8isCLkVThokm3347lKYL4IoL7jOiIeuUDb9ZVJbUDnOkK5/3NSbwo9PQj1DBVOJspLIPd3P8Ee5nYrj2ZiDcyiVrSGGxSvel/YD", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [#"Aircraft number" = _t, #"Maintainance Task" = _t]),
    #"Changed Type" = Table.TransformColumnTypes(Source,{{"Aircraft number", Int64.Type}, {"Maintainance Task", type text}}),
    #"Added Custom" = Table.AddColumn(#"Changed Type", "Order", each if Text.StartsWith ( [Maintainance Task], "OPEN" ) then 3 else if Text.StartsWith ( [Maintainance Task], "MSG" ) then 2 else 1, Int64.Type),
    #"Sorted Rows" = Table.Sort(#"Added Custom",{{"Aircraft number", Order.Ascending}, {"Order", Order.Ascending}}),
    //   #"Replaced Value" = Table.ReplaceValue(#"Changed Type", each [Maintainance Task], each if Text.StartsWith ( [Maintainance Task], "OPEN-O" ) then [Maintainance Task] & "#(cr)" else [Maintainance Task] & " | ",Replacer.ReplaceValue,{"Maintainance Task"}),

    #"Grouped Rows" = Table.Group(
        #"Sorted Rows", 
        {"Aircraft number", "Maintainance Task"}, 
        {
            {"Text", each Text.Combine ( List.Transform ( [Maintainance Task], (e) => if Text.StartsWith ( e, "MSG READ OUT" ) then " | " & e else if Text.StartsWith ( e, "OPEN-O" ) then e & "#(cr)" else e ) ) , type text }
        }, 0, (x,y) =>
            Number.From ( not Text.StartsWith (x[Maintainance Task], "MSG READ OUT" ) and not Text.StartsWith (y[Maintainance Task], "MSG READ OUT" ) )
            )
in
    #"Grouped Rows"

RESULT:

Hi kulkarni21vinee, like this?

Output

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("bY5BDsIgFESvMmFdE/QGtR0KCfARPpqm6f2v0brQuHA97+XNthlr7dUMZpKsY8isCLkVThokm3347lKYL4IoL7jOiIeuUDb9ZVJbUDnOkK5/3NSbwo9PQj1DBVOJspLIPd3P8Ee5nYrj2ZiDcyiVrSGGxSvel/YD", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [#"Aircraft number" = _t, #"Maintainance Task" = _t]),
    Ad_h = Table.AddColumn(Source, "h", each Text.Combine({[Aircraft number], Text.From(Byte.From(Text.StartsWith([Maintainance Task], "OPEN-O")))}, "_"), Int64.Type),
    AddedIndex = Table.AddIndexColumn(Ad_h, "Index", 0, 1, Int64.Type),
    GroupedRows = Table.Group(AddedIndex, "h", {{"Aircraft number", each List.First([Aircraft number]), Int64.Type}, {"Maintainance Task", each Text.Combine([Maintainance Task], if Text.StartsWith([Maintainance Task]{0}?, "OPEN-O") then "#(lf)" else "|") , type text}, {"Index", each List.First([Index]), Int64.Type}}, 1,
        (x,y)=> Value.Compare(y, x) ),
    SortedRows = Table.Sort(GroupedRows,{{"Index", Order.Ascending}}),
    RemovedColumns = Table.RemoveColumns(SortedRows,{"Index", "h"})
in
    RemovedColumns

Thanks for reaching out to the Microsoft Fabric Community Forum.

Regarding your query about the  Combine text on condition. We just wanted to confirm that the solution provided by ronrsnfld  is correct and should help resolve the issue you're facing.

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