Archicad library modifier

A few years ago I wrote a small Python app that goes through a big series of xml files, extracts specific parameters and displays them for modification. The app then allows for the creation of a json file that stores the changes made for future modifications (the xml file are from a 2d and 3d object library for Archicad that needs to be modified every year or two years). The numbers that need to be modified are attributes IDs (fills, line types, hatch types, materials, ...).

I need someone to rewrite this app in flutter with a nice and simple UI.
It needs to be light and easy to maintain in the future.
It needs to run on Mac and Windows.

You'll find in attachment :
1) the python app I created a few years ago
2) The original python code (not the last one, I lost it...)
3) A small sample of XML files in their original folder structure

The 5 attributes that need to be extracted :
<LineType> ("Line types" tab)
<PenColor> ("Pen colors" tab)
<FillPattern> ("Fill patterns" tab)
<BuildingMaterial> ("Building material" tab)
<Material> ("Surface" tab)

The attributes should be extracted with their respective "Description" (without the CDATA, only the text) and "Value" :

<PenColor Name="gs_pen_2D">
<Description><![CDATA["Stylo du symbole"]]></Description>
<Fix/>
<Flags>
<ParFlg_Child/>
</Flags>
<Value>3</Value>
</PenColor>

They should be grouped in separate tabs (5 tabs, one for each attribute) and displayed by their respective "Description" and "Value". There should be an uneditable "Original value" column and an editable "New value" column. The "New value" column should be editable by loading an existing json or CSV file. It should be possible to save a json or csv file with the new values entered on the app.

Then a simple button will parse every XLM file replace every "Value" that needs to be modified and save the modified XL files in the same place without modifying anything else in the files.