Lumen can sit in your taskbar with a real icon and open in its own window, like any other app on your computer. It takes about ten seconds. Here is why it is worth doing, and then exactly how.
It opens in its own window
No tabs, no address bar. Lumen stops being the tab you lose behind twenty other tabs.
Reminders can reach you
An app that is actually open can tell you a session is due. A closed tab cannot.
One click from your taskbar
Your icon sits with the rest of your apps, and switching to Lumen works the same way switching to anything else does.
On this computer
Click the three dots at the top right of your browser.
Hover over "Cast, Save, and Share".
Click "Install page as app", then confirm.
If "Install page as app" is greyed out, you are on a tab that is not a website, like a saved file or a settings page. Come back to this tab first and it will be black again. Some versions of Chrome word it "Create Shortcut" instead, and there you also want to tick "Open as window".