No that class in the base class libraries is not extensible. You should create your own form/dialog. A few examples:
https://www.codeproject.com/Articles/601900/FlexibleMessageBox-A-flexible-replacement-for-the
https://community.idera.com/database-tools/powershell/powertips/b/tips/posts/creating-simple-custom-dialog
https://docs.microsoft.com/en-us/powershell/scripting/samples/creating-a-custom-input-box?view=powershell-7.1
Add-Type -AssemblyName System.Windows.Forms
Add-Type -AssemblyName System.Drawing
$form = New-Object System.Windows.Forms.Form
$form.Text = 'Data Entry Form'
$form.Size = New-Object System.Drawing.Size(500,200)
$form.StartPosition = 'CenterScreen'
$form1.Font = New-Object System.Drawing.Font($form1.font.Name,14)
$okButton = New-Object System.Windows.Forms.Button
$okButton.Location = New-Object System.Drawing.Point(75,120)
$okButton.Size = New-Object System.Drawing.Size(75,23)
$okButton.Text = 'OK'
$okButton.DialogResult = [System.Windows.Forms.DialogResult]::OK
$form.AcceptButton = $okButton
$form.Controls.Add($okButton)
$cancelButton = New-Object System.Windows.Forms.Button
$cancelButton.Location = New-Object System.Drawing.Point(150,120)
$cancelButton.Size = New-Object System.Drawing.Size(75,23)
$cancelButton.Text = 'Cancel'
$cancelButton.DialogResult = [System.Windows.Forms.DialogResult]::Cancel
$form.CancelButton = $cancelButton
$form.Controls.Add($cancelButton)
$label = New-Object System.Windows.Forms.Label
$label.Location = New-Object System.Drawing.Point(10,20)
$label.Size = New-Object System.Drawing.Size(480,20)
$label.Text = 'Please enter the information in the space below:'
$label.Font = New-Object System.Drawing.Font($form1.font.Name,14)
$form.Controls.Add($label)
$textBox = New-Object System.Windows.Forms.TextBox
$textBox.Location = New-Object System.Drawing.Point(10,50)
$textBox.Size = New-Object System.Drawing.Size(460,20)
$textBox.Font = New-Object System.Drawing.Font($form1.font.Name,14)
$form.Controls.Add($textBox)
$form.Topmost = $true
$form.Add_Shown({$textBox.Select()})
$result = $form.ShowDialog()
if ($result -eq [System.Windows.Forms.DialogResult]::OK)
{
$x = $textBox.Text
$x
}