You can link Activities to other records adding their IDs into the activity Description with a preset prefix.
Patterns could include- CRMID:123 (replacing 123 for the ID of the record in question), - it will look something like this
This will also update next and last actions for any new linked records via this method. The prefix to use is controlled by the following setting:
Prefix for tag in description used to link activities to existing records by matching by ID
and defaults to "CRMID:".
This can be used from OpenCRM, or, for example if creating an activity from Jotform, or some other external source.