Use the built-in editor to edit the config file if vscode is not installed.

lib/pages/comic_source_page.dart

@@ -111,7 +111,6 @@ class _BodyState extends State<_Body> {
             trailing: Row(
               mainAxisSize: MainAxisSize.min,
               children: [
-                if (App.isDesktop)
                 Tooltip(
                   message: "Edit".tl,
                   child: IconButton(
@@ -165,7 +164,8 @@ class _BodyState extends State<_Body> {
             }
           } else {
             current = item.value['options']
-                .firstWhere((e) => e['value'] == current)['text'] ?? current;
+                    .firstWhere((e) => e['value'] == current)['text'] ??
+                current;
           }
           yield ListTile(
             title: Text((item.value['title'] as String).ts(source.key)),
@@ -249,6 +249,7 @@ class _BodyState extends State<_Body> {
   }
 
   void edit(ComicSource source) async {
+    if (App.isDesktop) {
       try {
         await Process.run("code", [source.filePath], runInShell: true);
         await showDialog(
@@ -266,11 +267,18 @@ class _BodyState extends State<_Body> {
                   },
                   child: const Text("continue")),
             ],
-              ));
+          ),
+        );
+        return;
       } catch (e) {
-      context.showMessage(message: "Failed to launch vscode");
+        //
       }
     }
+    context.to(() => _EditFilePage(source.filePath)).then((value) async {
+      await ComicSource.reload();
+      setState(() {});
+    });
+  }
 
   static Future<void> update(ComicSource source) async {
     if (!source.url.isURL) {
@@ -300,12 +308,14 @@ class _BodyState extends State<_Body> {
   }
 
   Widget buildCard(BuildContext context) {
-    Widget buildButton({required Widget child, required VoidCallback onPressed}) {
+    Widget buildButton(
+        {required Widget child, required VoidCallback onPressed}) {
       return Button.normal(
         onPressed: onPressed,
         child: child,
       ).fixHeight(32);
     }
+
     return SliverToBoxAdapter(
       child: SizedBox(
         width: double.infinity,
@@ -561,3 +571,51 @@ void _addAllPagesWithComicSource(ComicSource source) {
 
   appdata.saveData();
 }
+
+class _EditFilePage extends StatefulWidget {
+  const _EditFilePage(this.path);
+
+  final String path;
+
+  @override
+  State<_EditFilePage> createState() => __EditFilePageState();
+}
+
+class __EditFilePageState extends State<_EditFilePage> {
+  var current = '';
+
+  @override
+  void initState() {
+    super.initState();
+    current = File(widget.path).readAsStringSync();
+  }
+
+  @override
+  void dispose() {
+    File(widget.path).writeAsStringSync(current);
+    super.dispose();
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    return Scaffold(
+      appBar: Appbar(
+        title: Text("Edit".tl),
+      ),
+      body: Column(
+        children: [
+          Container(
+            height: 0.6,
+            color: context.colorScheme.outlineVariant,
+          ),
+          Expanded(
+            child: CodeEditor(
+              initialValue: current,
+              onChanged: (value) => current = value,
+            ),
+          ),
+        ],
+      ),
+    );
+  }
+}