Thanks for our help !
Finally, I asked Windows to reinit all its network configurations and 'ô miracle' I can see again my SMB shares on my PC.
Without understanding, I summarize:
0/ I have a Kodi configuration OK, SMB shares on my LAN OK. LAN access to Chorus or Emby interfaces OK. Ports 8080 or 8096 not exported to the public.
1/ I configure the redirection of ports to export them and allow a distant access. Distant access doesn't work.
2/ I disactivate SMB on Kodi and distant access start to work (at this step, I no longer see kodi SMB shares on my PC, which is normal).
3/ I reactivate SMB on Kodi and distant access is still OK but I still can't see kodi SMB shares on m PC.
4/ I reiniatilize Network configs on m PC and all is OK.
What I have to do now before going forward, is to secure the exported communication by adding certificates to Kodi (self-signed or using letsencrypt) as vaughng suggested, or by a VPN. My box also proposes a PPTP VPN which could work with tinc but I don't know yet how to configure them.