I saved a worksheet to a file and closed it. Said file now appears on the File > Reopen list.
Please let me know if you're doing something differently.
I do similar. In the same session it does appear in the reopen menu.
When sql developer is restarted,only the file I explicitly closed is in the reopen menu.
In previous releases files closed when quitting sql developer. Sounds like what I am noticing.
So when closing SQL Developer, files left open will be automatically re-opened on restart - that was a bug where it wasn't happening in earlier versions of v4.
It seems like the File > Reopen list may be including only worksheets saved as files, not any file that has been opened. Not sure if that is considered the correct behavior. Take a look at the View > Files > Recent Files node -- that may include all files, and apparently persists between sessions.