diff --git a/.gitignore b/.gitignore
index 186d286..a8b6570 100644
--- a/.gitignore
+++ b/.gitignore
@@ -14,6 +14,9 @@
 # production
 /build
 
+# node version manager
+/.nvmrc
+
 # misc
 .DS_Store
 .env.local
@@ -24,6 +27,3 @@
 npm-debug.log*
 yarn-debug.log*
 yarn-error.log*
-
-# plugin-zip
-/plugin-zip
diff --git a/.nvmrc.dist b/.nvmrc.dist
new file mode 100644
index 0000000..4a41167
--- /dev/null
+++ b/.nvmrc.dist
@@ -0,0 +1 @@
+12.20.0
diff --git a/package.json b/package.json
index f2d8cf0..3f1dbbc 100644
--- a/package.json
+++ b/package.json
@@ -18,8 +18,12 @@
     "react-select": "^3.1.0",
     "reactstrap": "^8.4.1"
   },
+  "engines": {
+    "node": "12.20.0",
+    "npm": "6.14.8"
+  },
   "scripts": {
-    "clean": "rm -rf plugin-zip && mkdir plugin-zip",
+    "clean": "git clean -fdxq -- ./plugin-zip/",
     "start": "npm run fix && node scripts/start.js",
     "build": "export CI=\"${CI-true}\" && npm run fix && CI=true npm run test && node scripts/build.js",
     "fix": "npm run translate && npm exec -- eslint --fix src/locale/lang",
@@ -27,7 +31,7 @@
     "translate": "node scripts/translate.js",
     "push-translate": "tx push -s",
     "pull-translate": "tx pull -a -f && npm run translate",
-    "build-plugin": "export GENERATE_SOURCEMAP=false && npm run clean && npm run build && node scripts/build-plugin.js"
+    "build-plugin": "export GENERATE_SOURCEMAP=false && npm run build && node scripts/build-plugin.js"
   },
   "browserslist": {
     "production": [
diff --git a/plugin-zip/.gitignore b/plugin-zip/.gitignore
new file mode 100644
index 0000000..1fee094
--- /dev/null
+++ b/plugin-zip/.gitignore
@@ -0,0 +1,12 @@
+# plugin-zip (build artefact folder)
+#
+# build output directory for the plugin zip archives
+#
+!/.gitignore
+
+# zips
+/*.zip
+
+# zip backups
+/*.zip~
+/*.zip.~?*~
diff --git a/scripts/build-plugin.js b/scripts/build-plugin.js
index 34e663b..e5079c9 100644
--- a/scripts/build-plugin.js
+++ b/scripts/build-plugin.js
@@ -8,6 +8,13 @@ const config = {
   dir: paths.appBuild + '/static/'
 };
 
+// verify zip output path against the file-system
+const zipPathFromZipFile = (file) => path.join(paths.zipPath, file);
+if (!fs.existsSync(zipPathFromZipFile('.'))) {
+  console.error(`fatal: paths.zipPath: '${paths.zipPath}' does not exists`);
+  process.exit(1);
+}
+
 const zip = new JSZip();
 
 // build file
@@ -49,7 +56,19 @@ zip.file('task/info.json', JSON.stringify(jsonFileContent, null, '  '));
 
 zip.generateAsync({type: 'nodebuffer'}).then(function(content) {
   let zip = `${pluginInfoContent.name}-${pluginInfoContent.version}.zip`;
-  fs.writeFile(paths.zipPath + '/' + zip, content, function(err) {
+  { /* do backups similar to cp(1) --backup=numbered */
+    const zipPath = zipPathFromZipFile(zip);
+    let number = 1;
+    let bakFile = zipPath + `.~${number}~`;
+    if (fs.existsSync(zipPath)) {
+      while (fs.existsSync(bakFile)) {
+        bakFile = zipPath + `.~${number++}~`;
+      }
+      console.log(`overwriting '${zip}' (backup: '${bakFile.replace(/^.*\/([^/]+)$/, '$1')}')`);
+      fs.renameSync(zipPath , bakFile);
+    }
+  }
+  fs.writeFile(zipPathFromZipFile(zip), content, function(err) {
     if (err) {
       console.log(zip + ' failed');
       console.log(err);
diff --git a/src/index.js b/src/index.js
index eebcd94..8bfc164 100644
--- a/src/index.js
+++ b/src/index.js
@@ -5,3 +5,12 @@ import './setting';
 
 ReactDOM.render(<App showDialog={true} key={(new Date()).getTime()} />, document.getElementById('root'));
 
+/**
+ * plugin development window.app shim (dtable-ui)
+ *
+ * @link https://docs.seatable.io/published/dtable-sdk/dtable-ui.md
+ */
+window.app = window.app ? window.app : {};
+window.app.expandRow = window.app.expandRow || ((row, rowTable) => {
+  console.log('dtable-ui shim: app.expandRow', [row, rowTable]);
+});