Thank you very much for your feedback. I started to work on a 'Help' section which is provided in the latest release of FlagCookies and I also tried to reword some of the information provided on the add on listing, as well as more meaningful tooltips.

The help or documentation can be viewed online at the FlagCookies wiki @ Github:
https://github.com/jrie/flagCookies/wiki/FlagCookies-help-and-documentation

At the moment of writing, this is work in progress. But I tried to provide a starting point inside there, about the basic "flag switches" and "modes" which are offered and where they might be possible used; so I gladly would invite to review this new addition.

Edit:
Is the issue you report reproduce able? Does this always occur?
Usually, the domain which got loaded should be displayed. I am also not sure which exact version you are using to get an insight if this was caused by another request interfering with what Flag Cookies thinks is the current active domain/tab you are on. But the issue might be resolved already in a later version.

In case you don't call a Github account your own, can you provide me with the urls of those two domains and the details which version you are using at the moment? You can drop me this information by email, using the support address and I try to troubleshoot the issue.
Or you can open an issue on Github instead.