Thanks for your report.
Closing WinSCP definitely disconnects it from the opened files.
But after you disconnect and reopen the same session again, if you then save the edited file, WinSCP should ask you:

Do you want to attach edited file '...' to session '...'?

Original session used to download file '...' to editor was closed already.

Can you post step-by-step instructions for reproducing a scenario in which the above "re-attach" does not happen?

There are 2 issues i am facing:
Issue 1:

• Login into session > open remote file in another editor (Notepad++)
  
• close WinSCP > Login again > now I see file already open in N++ is de-linked as I am not able save file and i have confirmed it by re-opening same file again from WinSCP and it is opening at another location ...AppData/Local/Temp/scp27268/ instead of old ...AppData/Local/Temp/scp19478/
  
• Login Session's details Hostname etc same always.
  

Issue 2:

• Login into session
  
• open remote file in another editor (Notepad++)
  
• remote disconnected due to network issue
  
• Login again with all same details except Hostname(ip) changed
  
• now I see file already open in N++ is de-linked as I am not able save file and I confirmed it by re-opening same file from WinSCP and it is opening at another location ...AppData/Local/Temp/scp31268/ instead of old ...AppData/Local/Temp/scp21478/
  

Is there any setting/solution to force specific login session to keep same Temp's dir and avoid above de-linking of previously opened remote files?

WinSCP v6.5.3