Adding a feedback provider from PS https://devblogs.microsoft.com/powershell/what-are-feedback-providers/

TestingFeedbackProvider.ps1

using namespace System.Management.Automation.Subsystem.Feedback
using namespace System.Management.Automation.Subsystem
using namespace System.Threading

param (
    # Just unregister the implementation
    [switch] $UnregisterOnly
)

class TestingFeedback : IFeedbackProvider {
    
    [Guid] $Id
    [FeedbackTrigger] $Trigger
    [string] $Name
    [string] $Description

    TestingFeedback() {
        $this.Id = [Guid]::new("230e5ee4-afa8-4319-9492-88239003f0e6");
        $this.Trigger = [FeedbackTrigger]::CommandNotFound
        $this.Name = "testing"
        $this.Description = "A feedback source for testing."
    }

    [FeedbackItem] GetFeedback([FeedbackContext] $context, [CancellationToken] $token) {
        if ($null -eq [runspace]::DefaultRunspace) {
            return $null
        }

        return [FeedbackItem]::new(
                "Testing testing...",
                [System.Collections.Generic.List[string]] @(
                    "1",
                    "2",
                    "3"
                ),
                [FeedbackDisplayLayout]::Portrait
        )
    }
}

# Check if the provider is already registered
$provider = [TestingFeedback]::new()
$existingRegistration = (Get-PSSubsystem -Kind "FeedbackProvider").Implementations | Where-Object {
    $_.Id -eq $provider.Id
}

# Re-add the provider to reflect code changes
if($null -ne $existingRegistration) {
    [SubsystemManager]::UnregisterSubsystem(
        [SubsystemKind]::FeedbackProvider,
        $provider.Id
    )
}
if(-not $UnregisterOnly) {
    [SubsystemManager]::RegisterSubsystem(
        [SubsystemKind]::FeedbackProvider,
        $provider
    )
    Write-Host -ForegroundColor Green "Registered '$($provider.Name)' as a FeedbackProvider"
}

It's close but having some issues.

PS> $PSVersionTable

Name                           Value
----                           -----
PSVersion                      7.4.0-preview.4
PSEdition                      Core
GitCommitId                    7.4.0-preview.4
OS                             Microsoft Windows 10.0.22000
Platform                       Win32NT
PSCompatibleVersions           {1.0, 2.0, 3.0, 4.0…}
PSRemotingProtocolVersion      2.3
SerializationVersion           1.1.0.1
WSManStackVersion              3.0

PS> Get-PSSubsystem | Where-Object { $_.Kind -eq "FeedbackProvider" } | Select-Object -ExpandProperty Implementations

Id                 : a3c6b07e-4a89-40c9-8be6-2a9aad2786a4
Kind               : FeedbackProvider
Name               : general
Description        : The built-in general feedback source for command errors.
ImplementationType : System.Management.Automation.Subsystem.Feedback.GeneralCommandErrorFeedback

Id                 : 230e5ee4-afa8-4319-9492-88239003f0e6
Kind               : FeedbackProvider
Name               : testing
Description        : A feedback source for testing.
ImplementationType : TestingFeedback

PS> Get-Module PSReadLine
ModuleType Version    PreRelease Name                                ExportedCommands
---------- -------    ---------- ----                                ----------------
Script     2.3.1      beta1      PSReadLine                          {Get-PSReadLineKeyHandler, Get-PSReadLineOption, Remove-PSReadLineKeyHandler, Set-PSReadLineKeyHandler…}