This feature was removed in 4.2.0. It actually never really worked properly since Joomla! 1.6 was released almost five years ago. The way Joomla! is written (ACL, categories etc) there are too many cross-dependencies which mean that you cannot restore just one extension. Furthermore the advent of "package", "library" and "files" extension types made it impossible to predict where things were placed on your site. Finally, the Instal from Web and the related changes made it outright impossible to properly detect updated extensions.
These restrictions can not be worked around. Between shipping a feature which we knew was broken and unfixable or completely removing the broken feature we chose the latter. If it's not working as intended, we fix it. If it can't be fixed, we kill it.
Nicholas K. Dionysopoulos
Lead Developer and Director
🇬🇷Greek: native 🇬🇧English: excellent 🇫🇷French: basic • 🕐 My time zone is Europe / Athens
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