Repeat Friday Data for Weekends and Holidays

Hello, MarkDonald 

let
    Source = your_table,
    type_date = Table.TransformColumnTypes(Source,{{"balanceDate", type date}}),
    g = Table.Group(type_date, "balanceDate", {{"bd", each _}, {"data", each true}}),
    all_dates = List.Dates(
        List.Min(g[balanceDate]), 
        Duration.TotalDays(List.Max(g[balanceDate]) - List.Min(g[balanceDate])),
        #duration(1, 0, 0, 0)
    ),
    tl = Table.FromColumns({all_dates}, {"balanceDate"}),
    combine = g & tl,
    sort = Table.Sort(combine,{{"balanceDate", Order.Ascending}, {"data", Order.Descending}}),
    f_down = Table.FillDown(sort,{"bd"}),
    expand = Table.ExpandTableColumn(f_down, "bd", {"Concat", "Balance"})[[balanceDate], [Concat], [Balance]]
in
    expand

MarkDonald in the end we just select the columns we need 

[[balanceDate], [Concat], [Balance]]

 other than this it's all in the code. Just walk through steps in PQ editor. Refer to MS site to get understanding. 

Actually, sorry, it isn't looking quite right, it seems to be duplicating for the dates that already exist, apart from the last.  I have stepped through and can see where it is duplicating the dates but can't really figure out how to make it work without this happening.  I can correct at the end by simply removing duplicates so I have something that works, so thanks!  This is how I inserted your code: 

let
Source = Excel.CurrentWorkbook(){[Name="Table17"]}[Content],
#"Changed Type" = Table.TransformColumnTypes(Source,{{"balanceDate", type datetime}, {"Concat", type text}, {"Balance", type number}}),

type_date = Table.TransformColumnTypes(Source,{{"balanceDate", type date}}),
g = Table.Group(type_date, "balanceDate", {{"bd", each _}, {"data", each true}}),
all_dates = List.Dates(List.Min(g[balanceDate]), Duration.TotalDays(List.Max(g[balanceDate]) - List.Min(g[balanceDate])),#duration(1, 0, 0, 0)),
tl = Table.FromColumns({all_dates}, {"balanceDate"}),
combine = g & tl,
sort = Table.Sort(combine,{{"balanceDate", Order.Ascending}, {"data", Order.Descending}}),
f_down = Table.FillDown(sort,{"bd"}),
expand = Table.ExpandTableColumn(f_down, "bd", {"Concat", "Balance"})[[balanceDate], [Concat], [Balance]]
in
expand

balanceDateConcatBalance