I tried to add the previously created Compose ECG widget inside the standard card widget, adding to the latter minimal controls for the rendering procedure: start/stop and changing the rendering mode.
The application has acquired a slightly more decent appearance and similarity to applications in Java (https://github.com/mk590901/java_graph_widget_viewer) and Kotlin (https://github.com/mk590901/Kotlin-ECG-Widget-Viewer). You can see this below.