How to combine accounts or transfer all activation keys

Do you mean subscriptions, or serial numbers?

i'm not sure if you can do that, but if it's possible you'll need the help of adobe support.

using a browser that allows popups and cookies, contact adobe support during pst business hours by clicking here, https://helpx.adobe.com/contact.html

click contact us (= cryptic icon in the lower right)

in the chat field, type AGENT
be patient, it can take quite a while to reach a human