Important Note:
While this could have been lumped into CHD-736 which deals with merging tickets based on a slave/master context. It has been suggested in the corresponding forum thread that this could potentially serve as the foundation or starting point for developing a revised merget ticket solution.

I tend to agree with these sentiments, but more importantly this should be an independent request based on the fact that is a more generic (or abstract) merge ticket feature. To me it seems like even if we don't choose to implement a more robust merge ticket system based on slave/master for example, we could still implement this to satisfy a select group of users.

The original forum thread has much more details and information on how and why implementing this would be extremely beneficial (and could possibly solve other "merge ticket" design issues). So if you need more suggestions and justifications from users like pk4, please see the following:

http://www.cerb4.com/forums/showthread.php?p=7448#post7448

CHD-911 and CHD-917 stemmed from the same forum thread regarding a revised merge ticket system.

http://www.cerb4.com/forums/showthread.php?p=7506#post7506

http://www.cerb4.com/forums/showpost.php?p=9475&postcount=3

(quote)
If for example a client is having an issue with licensing for a server side product. I open up a different ticket, send it off to the vendor, and update the client ticket with either a subject prefixed of the Ticket ID (of the vendor) or make an internal comment on the client's ticket.

I think what would be best for the request (if implemented) would be something similar to JIRA's method.

For example, this JIRA request (http://www.wgmdev.com/jira/browse/CHD-911) has a simple "This issue is related to:" followed by a list of IDs. This may be added to Cerberus's helpdesk.

Or another idea (simpler) would be to hyperlink any Mask IDs in a staff comment over to that ticket - like JIRA does. From the example above, if you enter in any JIRA id as a comment, it automatically links it to that JIRA request. Same could be done with Mask IDs on comments.
(end quote)

I pointed some recent threads to this issue which seemed like the natural place. But since we don't appear to be attached to this "merge" idea, I think we could simply point people to using 'custom fields' to link up tickets. If they just copy the ticket's URL into a single-line text field, that will probably be a good alternative.

Right now it's not the best option simply because the custom fields do not parse URL-like text into clickable links. But that idea was filed a while back as CHD-1105 and is scheduled for an upcoming release.

Here is a potential implementation of this idea that is much more specific.

CHD-1174
[Tickets] Allow users to link related tickets via ticket IDs in comments or custom fields

This was implemented with the introduction of the ticket chooser on ticket merge.