Manually tag an EWS/CTA/Scorecard to Timeline activities (existing or new)

I need an option to tag an open CTA / Success Plan Objective / Scorecard Measure to either an existing timeline activity OR to a new activity being created from the General/Company 360 Timeline tab.

Example:

Currently the only way these associations work is if someone creates a new Timeline activity from the Timeline tab available in the preview of the CTA/Scorecard measure.

Not having this option makes it impossible to associate outbound emails (which are logged via the email to timeline or via Gainsight Assist) with any CTA / Scorecard measure.