How to add tab in Dashboard

Task:

You need to add tab in Courses section of dashboard which should show only Canceled courses (or courses with any other status). The same approach can be used to add tabs in other places of dashboard site.

Solution:

Edit page. Each tab on this page is a separate web part. And there is a Tabs web part, which makes web parts be shown as tabs.

You need to export one of the web parts, for example All:

save exported file in your PC.

Open REM site collection of your Dashboard subsite, open REM Site Settings, go to Web parts Gallery:

upload exported earlier web part, change Title and Name as you wish:

Go back to Dashboard subsite, Courses section. Edit page. Click Add a Web Part. You'll find uploaded earlier web part in Miscellaneous section:

Add this web part.

Click Edit Web Part for just added web part:

In Miscellaneous section set Registration Status to Canceled (status title may differ from UI presentation, contact support for other statuses' titles).
NOTE: Only one status can be set in Registration Status web part property. Statuses cannot be listed by any delimiter.

The order of tabs is controlled by Zone Index property (integer number from 0 = tabs from left to right). 
NOTE: Tabs web part should have the highest zone index.
In Layout section of web part's settings change Zone Index as desired:

Also change Title of web part in Appearance section.

Afterwards you need to delete Tabs web part, add it again (from Dashboard section), set highest Zone Index (set 30 for example) and checkbox "Show item count per tab":