Question

the system is hopeless, if accidental merged can not be cancelled, you have to improve your system

Comments

Not hopeless at all. Because the history of a merged profile is preserved, if a mistake is made the merged profile can be restored.

Answer 1

Unfortunately you cannot undo a merge. You will need to re-create the profile that was merged away.

See this G2g thread https://www.wikitree.com/g2g/831392/how-to-undo-a-merge

PS: You can copy (and paste) what is in the changes tab for the merged away profile when you re-create a new one on that merged away profile by mistake.  

Answer 2

In the changes tab,you can take the merge back, but follow directions there.

Comments

You can undo bio changes on the changes tab but you can't take the merge back.

Answer 3

The system is actually very good, having been fine tuned over a number of years. It just needs great care taken to only merge when you are absolutely sure, through very robust sourcing and double-checking every step you make, before completing the final merge. As you have found, if you make a mistake with merging it cannot be undone.