Uneven rows separate with special characters "@" should transposed to one row

If your data looks like this:

Please find the VBA Code to accomplish your task below.  I have commented it for better understanding:

Sub Test()

    Dim LngLp As Long
    Dim ShrtLp As Integer
    Dim SrcSht As Worksheet
    Dim DestSht As Worksheet
    Dim ColCounter As Integer
    Dim SrcLrow As Long
    Dim DestLrow As Long
    
    Set SrcSht = Sheets("Before") 'Define Worksheet
    Set DestSht = Sheets("After") 'Define Worksheet
    SrcLrow = SrcSht.Cells(Rows.Count, "A").End(xlUp).Row 'Define Source LastRow
    
    'Cycle through column A on Source SHeet and look for @
    For LngLp = 1 To SrcLrow
        If SrcSht.Cells(LngLp, "A") = "@" Then 'If we find an @ move data to After Worksheet
        DestLrow = DestSht.Cells(Rows.Count, "A").End(xlUp).Row 'Define Destination Sheet Last Row
        For ShrtLp = LngLp + 1 To SrcLrow
            If SrcSht.Cells(ShrtLp, "A") <> "@" Then 'Identify if this is the last field in the address
                ColCounter = ColCounter + 1 'We need to increment columns in order to make sure the data is moved correctly
                DestSht.Cells(DestLrow + 1, ColCounter) = SrcSht.Cells(ShrtLp, "A")
            Else
                LngLp = ShrtLp - 1 'Reset the LngLp Value to start on the next address
                ColCounter = 0 'Reset Column Counter
                Exit For
            End If
        Next ShrtLp
        End If
    Next LngLp

End Sub

Another variant is with Power Query

Generated script

let
    Source = Excel.CurrentWorkbook(){[Name="Table1"]}[Content],
    AddIndex = Table.AddIndexColumn(Source, "Index", 0, 1),
    IndexSeparator = Table.AddColumn(AddIndex, "Custom",
        each if [Column1] = "@" then [Index] else null),
    IndexGroups = Table.FillDown(IndexSeparator,{"Custom"}),
    RemoveSeparator = Table.SelectRows(IndexGroups, each ([Column1] <> "@")),
    GroupTexts = Table.Group(RemoveSeparator, {"Custom"},
        {{"Combined", each Text.Combine([Column1], " "), type text}}),
    KeepIt = Table.SelectColumns(GroupTexts,{"Combined"})
in
    KeepIt