If you've removed the floating button of Page Marker carelessly, a Page Marker notification icon will show up on the status bar. This only appears if Google Chrome is running on the foreground. Re-launch floating button of Page Marker as the following steps:
Swipe down the status bar.
Tap the Page Markernotification ,and Its floating button will then appear again on the screen of Chrome.
Note: The Page Marker floating button and Page Marker icon on the status bar will NOT appear if Page Marker is turned off at the setting page and if Google Chrome is not running on the foreground.
You can again turn on Page Marker floating button/notification icon from below settings:
Go to Settings > ASUS customized settings > Page Marker.
Activate Turn on floating button to show the Page Marker button on the screen or icon on the status bar when using Google Chrome.