Because there are many times problems caused by a non-empty cache, it would be nice, in case you use an external browser, that this browser opens the album a new incognito window.

Can that automatically be done by jAlbum or can I get that now already be done by a setting in the (Chrome-) browser?

Fo Chrome desktop https://chrome.google.com/webstore/detail/tab-switcher/gcilookdakgpccpbcjgnpaecofklimck

According to https://superuser.com/questions/1314881/chrome-private-tabs-to-regular-tab
It should do what you want, ‘When you press the Incognito Tab Switch button, it opens up your current tab in an incognito window. Keep pushing the button, and each tab gets added to the new incognito session. If you enable the extension to work in incognito mode, you can also switch those tabs back to normal browser tabs with a click.’

Of course, you can simply copy the url from the normal tab, open a private tab and paste.

I start Chrome in incognito mode with this link:

"C:\Program Files\Google\Chrome\Application\chrome.exe" -incognito

Is it not possible to enter such a string under Preferences and use that string to start the browser?
If that field is empty you could start the default browser as you do now.