diff --git a/core/modules/startup/render.js b/core/modules/startup/render.js
index 05ba9844d..fc93bcdb3 100644
--- a/core/modules/startup/render.js
+++ b/core/modules/startup/render.js
@@ -106,6 +106,8 @@ exports.startup = function() {
 	// Fix up the link between the root widget and the page container
 	$tw.rootWidget.domNodes = [$tw.pageContainer];
 	$tw.rootWidget.children = [$tw.pageWidgetNode];
+	// Run any post-render startup actions
+	$tw.rootWidget.executeStartupTiddlers("$:/tags/StartupAction/PostRender");
 };
 
 })();
diff --git a/core/modules/startup/startup.js b/core/modules/startup/startup.js
index ad1416bf3..b7897a5ce 100755
--- a/core/modules/startup/startup.js
+++ b/core/modules/startup/startup.js
@@ -64,17 +64,12 @@ exports.startup = function() {
 		document: $tw.browser ? document : $tw.fakeDocument
 	});
 	// Execute any startup actions
-	var executeStartupTiddlers = function(tag) {
-		$tw.utils.each($tw.wiki.filterTiddlers("[all[shadows+tiddlers]tag[" + tag + "]!has[draft.of]]"),function(title) {
-			$tw.rootWidget.invokeActionString($tw.wiki.getTiddlerText(title),$tw.rootWidget);
-		});
-	};
-	executeStartupTiddlers("$:/tags/StartupAction");
+	$tw.rootWidget.executeStartupTiddlers("$:/tags/StartupAction");
 	if($tw.browser) {
-		executeStartupTiddlers("$:/tags/StartupAction/Browser");		
+		$tw.rootWidget.executeStartupTiddlers("$:/tags/StartupAction/Browser");		
 	}
 	if($tw.node) {
-		executeStartupTiddlers("$:/tags/StartupAction/Node");		
+		$tw.rootWidget.executeStartupTiddlers("$:/tags/StartupAction/Node");		
 	}
 	// Kick off the language manager and switcher
 	$tw.language = new $tw.Language();
diff --git a/core/modules/widgets/widget.js b/core/modules/widgets/widget.js
index e0444573d..bd66438e2 100755
--- a/core/modules/widgets/widget.js
+++ b/core/modules/widgets/widget.js
@@ -571,6 +571,16 @@ Widget.prototype.invokeActionString = function(actions,triggeringWidget,event,va
 	return widgetNode.invokeActions(this,event);
 };
 
+/*
+Execute action tiddlers by tag
+*/
+Widget.prototype.executeStartupTiddlers = function(tag) {
+	var self = this;
+	$tw.utils.each(self.wiki.filterTiddlers("[all[shadows+tiddlers]tag[" + tag + "]!has[draft.of]]"),function(title) {
+		self.invokeActionString(self.wiki.getTiddlerText(title),self);
+	});
+};
+
 Widget.prototype.allowActionPropagation = function() {
 	return true;
 };
diff --git a/editions/tw5.com/tiddlers/features/StartupActions.tid b/editions/tw5.com/tiddlers/features/StartupActions.tid
index 3b5583f47..79a23b3d9 100644
--- a/editions/tw5.com/tiddlers/features/StartupActions.tid
+++ b/editions/tw5.com/tiddlers/features/StartupActions.tid
@@ -1,16 +1,21 @@
 created: 20180323092308399
-modified: 20190307183936035
+modified: 20201025161723719
 tags: Features
 title: StartupActions
 type: text/vnd.tiddlywiki
 
 TiddlyWiki executes any ActionWidgets found in tiddlers with the following system tags during startup:
 
-* <<tag "$:/tags/StartupAction">> (executed on all platforms)
-* <<tag "$:/tags/StartupAction/Browser">> (only executed when running in the browser)
-* <<tag "$:/tags/StartupAction/Node">> (only executed when running under Node.js)
+* Executed during initial startup:
+** <<tag "$:/tags/StartupAction">> (executed on all platforms)
+** <<tag "$:/tags/StartupAction/Browser">> (only executed when running in the browser)
+** <<tag "$:/tags/StartupAction/Node">> (only executed when running under Node.js)
+* Executed after startup rendering:
+** <<.from-version "5.1.23">> <<tag "$:/tags/StartupAction/PostRender">> (only executed when running in the browser)
 
-Startup actions are useful for customising TiddlyWiki according to environmental factors such as the screen size. For example, the following action widgets when placed in a tiddler tagged `$:/tags/StartupAction/Browser` will cause the sidebar to be hidden by default when the screen width is less than 1000 pixels:
+!! Initial Startup Actions
+
+The initial startup actions are useful for customising TiddlyWiki according to environmental factors such as the screen size. For example, the following action widgets when placed in a tiddler tagged `$:/tags/StartupAction/Browser` will cause the sidebar to be hidden by default when the screen width is less than 1000 pixels:
 
 ```
 <$reveal type="lt" state="$:/info/browser/screen/width" text="3000">
@@ -28,8 +33,12 @@ Startup actions are useful for customising TiddlyWiki according to environmental
 <$action-setfield $tiddler="$:/language" text={{{ [[$:/languages/en-GB]] [plugin-type[language]sort[description]removeprefix[$:/languages/]] +[prefix{$:/info/browser/language}] ~[[en-GB]] +[addprefix[$:/languages/]] }}}/>
 ```
 
-Note that global macros are not available within startup action tiddlers by default. If you need to access them then you'll need to explicitly include them with an ''import'' [[pragma|Pragma]] at the top of the tiddler:
+Note that global macros are not available within initial startup action tiddlers by default. If you need to access them then you'll need to explicitly include them with an ''import'' [[pragma|Pragma]] at the top of the tiddler:
 
 ```
 \import [[$:/core/ui/PageMacros]] [all[shadows+tiddlers]tag[$:/tags/Macro]!has[draft.of]]
 ```
+
+!! Post-Render Startup Actions
+
+<<.from-version "5.1.23">> Post-render startup actions occur after the TiddlyWiki user interface has been rendered. This makes it possible to perform actions that depend on the rendered display (such as displaying modals).