Let us start here, from square one. No, from Zero!

overlay/windows/card_manager.h

@@ -0,0 +1,33 @@
+#pragma once
+
+#include "overlay/window.h"
+
+namespace overlay::windows {
+
+    struct CardEntry {
+        std::string name = "unnamed";
+        std::string id = "E004000000000000";
+        bool selected = false;
+    };
+
+    class CardManager : public Window {
+    public:
+
+        CardManager(SpiceOverlay *overlay);
+        ~CardManager() override;
+
+        void build_content() override;
+
+    private:
+
+        std::string config_path;
+        bool config_dirty = false;
+        std::vector<CardEntry> cards;
+        char name_buffer[65] {};
+        char card_buffer[17] {};
+
+        CardEntry *cards_get_selected();
+        void config_load();
+        void config_save();
+    };
+}