Redmine

You can create a new status named "ToMerge". Just go
in Admin -> Issue tracking -> Issue statuses.

I can't see how custom fields could be usefull for statuses.
Do you just need to add a "description" field for each
status ?

A description would be nice to have documentation for
site-specific stuff inside the issue tracker itself.

A site-specific status might be the one I wrote. Maybe more
formal like "Issue resolved in development branch. Will be
merged into the production branch next Merge Day, resolving
the issue. Merge Days are the third wednesday of every
month."

Or WaitCPU with description "Waiting for CPU cluster to be
available".

Some systems use "Pending". It's not always clear what
that
means. In this case "Pending" meant "Pending
clarification
or other data from customer".

So a description field would do, yes.

+1 on adding a description field to the statuses.

More Description fields in general would be useful.

See related Issue #6964, descriptions fields for roles, and descriptions for workflows/trackersd would be useful also.

Well, in my opinion, this could be closed. You can define some custom fields like you want.
Just add some custom field to your ticket as status description and everything should be fine, doesn't it? :)

I think instead of having custom fields on issue statuses - what is more desirable is to have contextual help framework which tells users "what to do" depending on the status of the issue (for every field).

See Related #2568, #705, #442 for more information.