I would like to request a new feature in firefox that would allow users to add private tabs in the same window without having to open a new window. This would be more convenient and efficient for managing private browsing sessions.
Thanks @sussybaka - can you say a little more there about the convenience aspects?
Separate windows allow for a clearer distinction between private and non private contexts - would you like private tabs inside normal windows just so that they don't get added to your browing history or rather to get increased privacy protections within them (sometimes at the expense of more breakage)?
You can have private tabs in the same window as your regular tabs by installing Temporary Containers and then enabling Delete History in its advanced settings.
If you consider human factors and usability, I must say that mixing private and normal tabs in the same window is a bad idea, unless it were to be implemented with some sort of drastic colour change or tedious warning every time the private/non-private active tab state switches...
The "Temporary Containers" add-on faces the same issue and as such gives you the warning before activating "Delete History": "[...]if you visited the same website URL in another Container, Temporary Container or in the Default Container before or while visiting it in a 'Deletes History Temporary Container' then those visits will get deleted from history too."
Why private tabs in addition to private windows? The reason we have tabs in the first place, is, so we don't have to switch between windows all the time. Tabs are easily accessible. If your browsing style includes often browsing in private mode and in non-private mode in parallel, then having to constantly switch windows is a hassle. I do this, because I like to keep a browsing history, but i also want a lot of e.g. trivial googling not to be included in it.
Tabs could easily show their status of being private or not with a symbol, or with a theme change (as is even done by default in private windows), so it really wouldn't be difficult to distinguish if a tab is private or not. If anything, adding an API so extensions can properly bring that functionality would be great.
I agree if private tabs will be made, they will should be a very visually distinguished otherwise i think it would be better to not add such a feature, since the possibility of human errors (entering something into a non-private tab when he/she doesnt want it) could be to high.