Moving companies where I have owner access
You can just add a collaborator to the company (Company Settings > Collaborators), with the email of your other account. Then you can log out and log in with the other account, and accept the invitation in app.ledgy.com/invitations.
Moving investment firms
Similar to moving companies, you can just add your other account as a collaborator (see above).
Moving your personal portfolio
Moving your personal portfolio requires a few more steps. The easiest is to create a temporary investment firm, move the investments from your personal portfolio to the investment firm, then proceed with "Moving investment firms" described above, and finally in the new account move the companies back to your personal portfolio.
Read more about how to move investments between your personal portfolio and investment firms.
Delete the account you will not be using anymore
1. Log in to the account
2. On the top right, click on your username and then Settings
3. Click on Permanently delete my account