that is better than my suggestion as it allows to have full session functionality aka unsaved files for both accounts.
Good one :-)

Eko

you could also use a single portable version that resides in a folder you can put anywhere (except inside %programfiles% or %programfilesx86%)

this way you could open the same session files, regardless if this portable notepad++.exe is started as a restricted user or as an administrator (elevated).
(only prerequisite is that both users have the same available paths and at least read permission to access all the files listed within this session … files without read permissions will not be reopened and purged from the session list)

basic explanation:
the portable np++ version confines all internal data including sessions to it’s own folder, so they are persistent to all users that have permission to read and write to this portable np++ folder.
this behaviour is triggered by the presence of an empty DoLocalConf.xml file.
the installed version on the other hand will write and read specific np++ internal data and settings inside different locations within the %homepath% of the user account that np++ has been started with

feel free to download and try the portable np++ version from this location:
https://notepad-plus-plus.org/repository/7.x/7.6/npp.7.6.bin.zip
(it will not interfere with your current installation)

sorry, but as far as I understand, the last instance is triggering writing the session information only.
So the only workaround I see at the moment is to create an independent shortcut and using a session file
and every time before you close this instance you want to save the session explicitly.

Eko