So I've searched for a while and found several answers but I don't want to take a chance with the wrong command and wipe data so I'd like instructions specific to my case please.
I resized my Windows7 partition with GParted which left 12Gb free. I then used a command in Terminal to reclaim that space in the APFS Container, operation was successful but then the volume briefly appeared under "External" ... I rebooted and now its gone.
disk0s2 is the High Sierra volume, is it possible to reactivate that partition without losing the Windows one ?
UPDATE : So klanomath fixed the problem with the APFS partition but the Windows one while visible remains "unbootable". I ran a Windows RE a few times which fixed things supposedly (last pass it said everything was fine) but when I press Alt at startup the partition isn't showing. When I select the volume from the Startup panel in System Preferences it just reboots to a black screen (no error just prompt)...
New state :