Chrome extension helps to display the timestamp in a readable format in the context menu (like "right mouse button"-menu). Just select the timestamp and open the context menu.

Try here:

• 1721911910854
• 1721911910

https://chromewebstore.google.com/detail/timestamp-converter/pmlnbfnennofecepkljclogbjobnmfce?pli=1

or raw install: download the entire repository folder and upload it to chrome extensions. Official google chrome the guide is here https://developer.chrome.com/docs/extensions/get-started/tutorial/hello-world#load-unpacked.