It might be possible beehind the scenes. Email email@example.com and ask the nice people there if they can do something.
If it’s an unofficial integration, then you might be able to just aim the new datapoints at the existing goal.
You can also email firstname.lastname@example.org with historical data, putting username/goalname in the subject, and the body with your datapoints in a format like
2018 12 01 1 "optional comment"
I just started using the official Clozemaster integration, and I confess to having started a new goal for that, rather than trying to preserve the history.
UPDATE: I exported the data from the old goal, reformatted it using Excel/Numbers and emailed the result to the bot with the new goal as the subject and the datapoints in the body. Used a formula something like
CONCATENATE(YEAR(A1)," ",MONTH(A1)," ",DAY(A1)," ",B1)