My previous thread on new bookmarks not being saved in Opera when using Sandboxie, was solved by adding a fix in Sandboxie.
This thread concerns login data (username and passwords) not being saved in Opera.
To fix this problem, do the following - bring up the SBxie Control Panel by right clicking the taskbar icon. Then follow - Sandbox>Default box>Settings>Resource access>File access>Direct access
Using Edit/Add, copy and paste each one of the following settings into the panel separately one after the other :-
opera.exe,%AppData%\Opera Software*\Login Data*
Then click Apply/OK. When entering the settings are visible in the panel, but when Apply is clicked, they disappear. No problem, this is OK.
Now, when Opera is shut down login data/password changes made during the session will be saved and on reopening with SBxie the changes will still show.