Powershell tools WPF older versions XAML vs code

A few years back I developed a WPF based PowerShell app that is used to process paper mailouts a couple of times a year. The PC that I developed it on died a month or so back. Since I created that App I have been working mainly on Linux, so my recollection as to how I put the app together is a bit hazy (yeah I know … keep notes!) So I created a new setup (based on Windows 11 rather than 10 for ease of new motherboard support) Firstly Visual Studio with tools won’t open the project. It says the project is incompatible

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On inspecting the various .ps1 files in the project there is a RTMinvocing.designer.ps1 file and this contains ps code to create all the WPF objects. So my (stupid) question is did I even create this with PS tools? Looking at the way it works now the designer creates a XAML file and then sucks it in. Did the WPF element of PS Pro tools work differently a few years back or did I use some other tool to create this app? I do vaguely remember playing around following some articles creating a XAML file in the C# project designer and copying it as a string into a test PS app , then I discovered a tool that would make life easier which I thought was PS Pro tools.