Power Query: remove all text between delimiters

There is an even simpler solution.

You can create a new function called fun_ReplaceTextBetweenDelimiters, and in it add this code 👇

let
    fun_ReplaceTextBetweenDelimiters = (Text as text, StartDelimiter as text, EndDelimiter as text, optional ReplaceDelimiters as nullable logical, optional NewText as nullable text, optional TrimResult as nullable logical, optional FixDoubleSpaces as nullable logical) as text => 
        let
            // Add Default Parameters
            Default_ReplaceDelimiters = if ReplaceDelimiters is null then true else ReplaceDelimiters,
            Default_NewText = if NewText is null then "" else NewText,
            Default_TrimResult = if TrimResult is null then true else TrimResult,
            Default_FixDoubleSpaces = if FixDoubleSpaces is null then true else FixDoubleSpaces,
            //Do work
            TextBetweenDelimiters = Text.BetweenDelimiters(Text, StartDelimiter, EndDelimiter),
            TextToReplace = if Default_ReplaceDelimiters then Text.Combine({StartDelimiter,TextBetweenDelimiters,EndDelimiter}) else TextBetweenDelimiters,
            ReplacedText = Text.Replace(Text, TextToReplace, Default_NewText),
            //Clean Result
            TrimmedText = if Default_TrimResult then Text.Trim(ReplacedText) else ReplacedText,
            FixedSpaces = if Default_FixDoubleSpaces then Text.Replace(TrimmedText, "  ", " ") else TrimmedText
        in
            FixedSpaces
in
    fun_ReplaceTextBetweenDelimiters

Then, we can test it like this:

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("i45WcnRyVtAw1FTSAbGUYnWilVzd3BU0jEAiQBZYJCIyCqhGRwEsCOQoxcYCAA==", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [TestData = _t, TargetData = _t]),
    ChangeType = Table.TransformColumnTypes(Source,{{"TestData", type text}, {"TargetData", type text}}),
    RunFunction = Table.AddColumn(ChangeType, "NewText", each fun_ReplaceTextBetweenDelimiters([TestData], "(", ")", true), type text),
    TestResult = Table.AddColumn(RunFunction, "Test", each [TargetData]=[NewText], type logical)
in
    TestResult

Input:

Output: