Add a status to your workflow, like adding a "Review" status for documentation updates, is essentially changing the workflow. To do this you should read the Working with workflows documentation, which will step you through adding a status, making sure you add transitions so that you can get to your new status, and give you more information on what you can do to that status to make it even more powerful. For instance, you may want to make sure that when you do move an issue to "Review", it's automatically assigned to a specific person. This can be achieved by adding a post function that allows you to update a specific field on an issue. Make the field the Assignee field, and select the specific person you want the issue assigned to. Bingo! The issue will now be assigned to the person when it's transitioned to that status. Take a look at Atlassian Answers, it's full of useful information.

Jira Core has one Assignee field, and this allows you to assign an issue to one person at a time. This is intentional, as it means one person is responsible for that piece of work. It stops the cases occurring where either two people are working on the same thing, or neither work on it as they think the other person is working on it! That being said, there's a few ways to achieve the concept above. You could split the issue into sub-tasks, and assign each sub-task to a different person. Another slightly more complex option is to add another field to the issue called a "user picker" field, which allows you to select other users. The Assignee of the issue is still responsible for the work, but it does mean other people can be added to the issue and will show as working on it. See the tip on assigning issues to a group below for more information!

 You can add additional fields to Jira Core's default issues, in fact you can even add additional issue types if you like. All this is covered in the Jira application administration documentation, just search for Adding a custom field. That'll walk you through which fields you can add to an issue, and how.

 Issue field security is something that a lot of organizations request, but it's not something we support in Jira Core. You can read more about that decision on this issue JRA-1330 - Getting issue details... STATUS .

You can set the security level on an issue however, visit the Jira application administration and search for Setting security on an issue for more information on that topic.

If you'd like to copy an issue, it's possible by using the Clone functionality. A cloned issue will create a link to the issue it's cloned from, and vice versa. You can read up on more details about issues and cloning them here.

Dashboards! Jira Core comes with a variety of gadgets that you can configure to show your information how you need to see it. You can add these gadgets to your dashboard,  and make that dashboard your homepage in Jira Core when you first log in. That way the first thing you'll see is the information that matters to you, and you'll know what you need to do.

Jira Core offers a powerful search function, and you can even save these searches as filters for use at a later stage. You can even share these filters with your team, so you're all looking at the same information. Keep on top of things together!

 Yes there is! Jira Core comes with the ability to add a label to an issue, and labels can be used in searches. In fact, the label is 'clickable' which means that when you click the label, you'll be taken to a search that shows all issues with that label. You can then refine that search if needed.

A word of caution though, check with your project administrator as to your organization's policy on using labels. There may be a policy in place regarding how this field should be used, as some organizations use it as part of a process.

 Jira Core is designed so that issues must be assigned to a single individual to prevent tasks from being overlooked. A team lead or manager should assign issues out to individuals, or your users will pick from a list of issues that they have the option to take on.

However, if you want to configure Jira Core to allow issues to be assigned to multiple users there are a few option for doing so:

It is easy to still setup a queue the a group can pick from, or affiliate an issue with group in addition to having it assigned to an individual within that group:

Managing Issues via a Queue

You can configure your Jira Core project to assign issues to an 'Unassigned' "queue" by default, which your users can then pick issues from.

To do this, set up the following:

1. Configure your Jira Core project to allow the 'default assignee' to be 'Unassigned'.
2. Ensure that 'Allow unassigned issues' is set to ON in your General Configuration settings (Administration > Global Settings > General Configuration).
3. Set any issues that you want to be in the queue to be 'Unassigned'.
4. Create a dashboard page with a filter that lists all 'Unassigned' issues, share the dashboard page and request that interested members of the group display the shared page on their dashboards.

Managing Issues via Group Ownership

You can add a custom field to store which users and groups should be associated with a given issue. This is particularly useful for projects where a team owns all issues of a particular type.

To do this, set up the following:

1. Add a group picker custom field to your issues.
2. Configure an email notification in your project's notification scheme to be sent to the 'Group Custom Field Value'.

An issue can now be "assigned" to the group by selecting the appropriate group in the group picker. An email notification will be sent to the group.

 Another option is to add a user picker custom field rather than a group picker, and assign multiple users to an issue. However, you will then have both the Jira Core default user field and custom user field for your assignees.

Managing Issues via a User Account

You can create a Jira Core user account to represent a group of people (e.g. 'developers') and assign issues to this user.

To do this, set up the following:

1. Create a Jira Core user to represent the group.
2. (Optional) Create an email mailing list for this group (not a Jira Core function) and set the mailing list email as the Jira Core user's email address.
3. Create a dashboard page showing issues assigned to this user, share the dashboard page and request that interested members of the group display the shared page on their dashboards.

An issue can now be assigned the new "user" representing the group and your users can track the issues on their dashboards. If you have set up a mailing list, your users will also be notified by email.

Managing Issue via Sub-Tasks

If you have a task managed by different users then you are able to break the combined task into individual subtasks with their own single assignees.

 Yes it is. Jira Core comes with two methods of grouping issues, Versions and Components. You can read more on these in the Administering a project section of the documentation. Essentially versions and components allow you to group issues, and the main distinction is that with a component you can assign a user as a default assignee when the component is added to the issue, and versions can have a start and end date.