I have two separate Firefox accounts, with separate emails to log in and their own sets of bookmarks, passwords, etc. I want to merge all the data from both of those into a single profile of a single account under just one of the emails. I'm pretty sure I've done this before, by: 1. Logging into account A and syncing. 2. Logging out of account A without deleting data. 3. Logging into account B and syncing. With the result that account B now contains all its original data plus all the data from account A. But when I just tried to do this process now, at the point of logging in to account B I got the error "Account limit reached for this profile. This profile was previously synced to a different account. To keep your data organised and secure, each Firefox profile can only be synchronised to one account. To sign in using [account B], create a new profile." I don't want to have separate profiles with the data from accounts A and B, I want it all merged into the same profile. How can I achieve this?