SOLUTION found: I was reluctant at first, but I guess we all have to lose sometimes.
Assuming that SMB 1.0 is enabled on all the computers (control panel/turn windows features on or off):
First ensure that all the computers are in the same Workgroup (Right click My Computer/Properties) and that all the connections are set to private (left click on the connection icon, choose the connection and click on the ! mark to choose Private). Ensure that network discovery and sharing are enabled.
Go to the folder you want to share, right click and choose "share". On the next menu, choose share with: everyone, and give permission to read and write.
The trick is to use a password or a pin on every computer even if you choose to share to everyone. Some computers require that you use the "share with command and follow the instructions on the next windows).
I hope it works for you.