(EDIT: I loved this addon, but I can't find any icon now in the customization window!). Maybe the dev changed it, because now it shows a text in the tab title, which is completely useless for me. I don't like having a prefix in my tabs title. I liked the icon and the text in the bar, indicating which was the profile used!

Anyway Profile switcher and all the addons to manage profiles are now dead! I don't know why all the profile management addons are dead in the recent Firefox version.

It was very useful before: I used it with Profile switcher, and with another custom icon (because the yellow icon is awful).