A few tweaks, with inspiration from Zeke :3

Signed-off-by: TheKodeToad <TheKodeToad@proton.me>

launcher/ui/pages/modplatform/CustomPage.h

@@ -0,0 +1,104 @@
+// SPDX-License-Identifier: GPL-3.0-only
+/*
+ *  PolyMC - Minecraft Launcher
+ *  Copyright (c) 2022 Jamie Mansfield <jmansfield@cadixdev.org>
+ *
+ *  This program is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, version 3.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ *
+ * This file incorporates work covered by the following copyright and
+ * permission notice:
+ *
+ *      Copyright 2013-2021 MultiMC Contributors
+ *
+ *      Licensed under the Apache License, Version 2.0 (the "License");
+ *      you may not use this file except in compliance with the License.
+ *      You may obtain a copy of the License at
+ *
+ *          http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *      Unless required by applicable law or agreed to in writing, software
+ *      distributed under the License is distributed on an "AS IS" BASIS,
+ *      WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *      See the License for the specific language governing permissions and
+ *      limitations under the License.
+ */
+
+#pragma once
+
+#include <QWidget>
+
+#include "ui/pages/BasePage.h"
+#include <Application.h>
+#include "tasks/Task.h"
+
+namespace Ui
+{
+class CustomPage;
+}
+
+class NewInstanceDialog;
+
+class CustomPage : public QWidget, public BasePage
+{
+    Q_OBJECT
+
+public:
+    explicit CustomPage(NewInstanceDialog *dialog, QWidget *parent = 0);
+    virtual ~CustomPage();
+    virtual QString displayName() const override
+    {
+        return tr("Custom");
+    }
+    virtual QIcon icon() const override
+    {
+        return APPLICATION->getThemedIcon("minecraft");
+    }
+    virtual QString id() const override
+    {
+        return "vanilla";
+    }
+    virtual QString helpPage() const override
+    {
+        return "Vanilla-platform";
+    }
+    virtual bool shouldDisplay() const override;
+    void retranslate() override;
+
+    void openedImpl() override;
+
+    BaseVersion::Ptr selectedVersion() const;
+    BaseVersion::Ptr selectedLoaderVersion() const;
+    QString selectedLoader() const;
+
+public slots:
+    void setSelectedVersion(BaseVersion::Ptr version);
+    void setSelectedLoaderVersion(BaseVersion::Ptr version);
+
+private slots:
+    void filterChanged();
+    void loaderFilterChanged();
+
+private:
+    void refresh();
+    void loaderRefresh();
+    void suggestCurrent();
+
+private:
+    bool initialized = false;
+    NewInstanceDialog *dialog = nullptr;
+    Ui::CustomPage *ui = nullptr;
+    bool m_versionSetByUser = false;
+    BaseVersion::Ptr m_selectedVersion;
+    BaseVersion::Ptr m_selectedLoaderVersion;
+    QString m_selectedLoader;
+};