Okay, I think I understand a little better.

Check out this feature idea:

Is that what you are talking about? If so, if enough people vote for it, Karbon will consider adding it to the roadmap.

I was looking for a more permanent solution.  I did not want to have to save to timeline each note or email.  And my colleague's emails from the individual timeline do not show up in the business timeline.    

@Terri Warren, that’s how we keep the emails organized on both timelines. Here’s a screenshot of the same note (works the same as email) on both the business and individual timelines:

The note also shows up on both work items.

Does that help at all, @Sharon Babin?

The problem is that Karbon only allows one owner and it doesn’t allow the same owner for both projects.

From the side tray, add the individual to the “add to timeline” area. 

Also, whichever email is indicated as the primary email (selecting the star) on the individual contact details tab will be the email address as that will auto add the email to the timeline as well.

@Sharon Babin 

I believe you would need to tag the email to both projects. I think, not certain, if the email address is identified as the primary for each customer (personal and business) it may also do that. Would suggest testing the latter one out. I believe I started doing that for a similar reason as I wanted all email from a particular email address to be visible on the timeline of each. Not sure if it extends to the work item or just the customers.