Removing Duplicate Strings from cells in a column

You can use the Table.TransformColumns function.

See the code below for an example:

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("i45WCi1OLXLNTczMUQgO8FNwdHRRwBBRitVBUofKI1bXYFQXCwA=", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [Resources = _t]),
    #"Changed Type" = Table.TransformColumnTypes(Source,{{"Resources", type text}}),
    
    #"Remove Duplicate Phrases" = Table.TransformColumns(#"Changed Type",{"Resources", each 
        Text.Combine(
            List.Distinct(
                Text.Split(_," ")
        ), " ")})
in
    #"Remove Duplicate Phrases"

or, since you wrote you have multiple tables, you can write it as a separate function, where you call it by specifying the Table and Column to process:

Add as blank query and rename eg: fnDeDupPhrases 

(tbl as table, col as text)=>

Table.TransformColumns(tbl,{col, each 
        Text.Combine(
            List.Distinct(
                Text.Split(_," ")
        ), " "), type text})

Then use like this

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("i45WCi1OLXLNTczMUQgO8FNwdHRRwBBRitVBUofKI1bXYFQXCwA=", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [Resources = _t]),
    #"Changed Type" = Table.TransformColumnTypes(Source,{{"Resources", type text}}),
    
    #"Remove Duplicate Phrases" = fnDeDupPhrases(#"Changed Type","Resources")

in
    #"Remove Duplicate Phrases"