Firefox Containers > Manage Containers > Remove [container]; message (modal, I think it's called?) pops up to say I have a tab open and do I want to proceed? I to up to the container icon upper-right, search for [container], click to open that page, then CTRL+W to close it. Then I try to Remove [container] again; fails. That container is still in the list, and still popping up a note that a tab is open in that container (no, I closed it). I really like the Containers feature, AND it could use some improvement. Unrelated, I'm open to help with proofreading; feel free to ask, or point me to a git where I could contribute. I'm not happy about the apparent erosion of privacy in Firefox, but it sure beats Google, Microsoft, Apple, etc.