Inno Setup CreateInputDirPage but don't check for folder existence

You cannot disable the validation.

You can workaround that by adding only three inputs using the .Add. And add the fourth input manually, taking control of it.

var
  DataDirPage: TInputDirWizardPage;
  CustomDirEdit: TEdit;

procedure InitializeWizard;
var
  Index: Integer;
  Offset: Integer;
  PromptLabel: TNewStaticText;
  UltimateEdit: TEdit;
  PenultimateEdit: TEdit;
  UltimateLabel: TNewStaticText;
begin
  DataDirPage := CreateInputDirPage(wpSelectDir,
    'FoldersSettings', 'Customize folders settings for non-standard EGPL systems',
    'If the defaults are acceptable, then click Next.',
    False, 'New Folder');

  DataDirPage.Add('GeoPackage Output Folder');
  Index := DataDirPage.Add('VHD Mount Path for GeoLibrarian');
  PenultimateEdit := DataDirPage.Edits[Index];
  Index := DataDirPage.Add('EGPL Source Folder');
  UltimateEdit := DataDirPage.Edits[Index];
  UltimateLabel := DataDirPage.PromptLabels[Index];

  Offset := UltimateEdit.Top - PenultimateEdit.Top;

  PromptLabel := TNewStaticText.Create(WizardForm);
  PromptLabel.Top := UltimateLabel.Top + Offset;
  PromptLabel.Width := UltimateLabel.Width;
  PromptLabel.Height := UltimateLabel.Height;
  PromptLabel.Parent := DataDirPage.Surface;
  PromptLabel.Caption := 'WWW Root Folder';

  CustomDirEdit := TEdit.Create(WizardForm);
  CustomDirEdit.Top := UltimateEdit.Top + Offset;
  CustomDirEdit.Width := UltimateEdit.Width;
  CustomDirEdit.Parent := DataDirPage.Surface;

  PromptLabel.FocusControl := CustomDirEdit;
end;

function NextButtonClick(CurPageID: Integer): Boolean;
begin
  Result := True;

  if CurPageID = DataDirPage.ID then
  begin
    if CustomDirEdit.Text = '' then
    begin
      MsgBox('You must enter WWW Root Folder.', mbError, MB_OK);
      Result := False;
    end;

    // Any other validation
  end;
end;

This does not feature the Browse button. It's yet more work and I'm not sure, if it makes sense, as the input is used to input a path to a drive that does not exist.