Hi,
after spending endless hours migrating data between dataverse environments & different accounts, I have developed a tool, the DX Cloner. The web based tool is used to move data (dataverse tables incl attachments) from A to B while automating the matching of lookups, GUID etc and. It automatically detects dependencies and guides you in the process of migration. You can find details here:
DX Cloner
After completing our own tests, I am now looking for some testers to collect more feedback and finetune the app. If you are interested, please sign up. I am happy to get in contact and explain the tool in more details as manuals etc do not exist yet.
KR
Sascha