Ubuntu – Try Ubuntu – Where does it store the files

You need to switch file browsers or submit a bug to have the feature re-added. The maintainers of that project decided to remove it for some (IMO) nonsense reason that I will likely never be convinced of.

Ranting aside your only options are to find a fork where someone put it back, like nemo, use a different file manager (there are several), or complain a lot in bug reports and mailing lists till the maintainers put it back or allow you to put it back (it is opensource after all).

Temporary files are usually stored in /tmp, and that's the case even for Archive Manager. Anyway it's not a good practice to batch remove them, since running applications might be using the folder to store temporary files necessary to their current instance to run (as it's the case for Archive Manager), and removing them could break the current instance. So you better either remove the files manually or just reboot, which automatically clears the folder.