Re-render when a new section is added

src/launcher.tsx

@@ -254,6 +254,9 @@ export class NewLauncher extends Launcher {
     this._favoritesDatabase = options.favoritesDatabase;
     this._settings = options.settings;
     this._newModel = options.model;
+    this._newModel.sectionAdded.connect(() => {
+      this.update();
+    });
   }
   private _lastUsedDatabase: ILastUsedDatabase;
   private _favoritesDatabase: IFavoritesDatabase;

src/model.ts

@@ -1,9 +1,15 @@
 import { INewLauncher, ISectionOptions } from './types';
+import { ISignal, Signal } from '@lumino/signaling';
 import { LauncherModel } from '@jupyterlab/launcher';
 
 export class NewModel extends LauncherModel implements INewLauncher {
+  sections: ISectionOptions[] = [];
   addSection(options: ISectionOptions) {
     this.sections.push(options);
+    this._sectionAdded.emit();
   }
-  sections: ISectionOptions[] = [];
+  get sectionAdded(): ISignal<NewModel, void> {
+    return this._sectionAdded;
+  }
+  private _sectionAdded = new Signal<NewModel, void>(this);
 }