You’re right, ctrl+alt+{left,right} works, but is interpreted by Ubuntu MATE as “switch workspace”. I would update my table, but unfortunately the site won’t allow me to 
The new table is:
| Shortcut | Purpose | Instead interpreted by | Instead does |
|---|---|---|---|
| shift+ctrl+n | new ticket | Chrome | new incognito window |
| shift+ctrl+w | close current tab | Chrome | immediately close Chrome |
| shift+ctrl+tab | next Zammad ticket tab | Chrome | previous Chrome tab |
| shift+ctrl+shift+tab [1] | previous Zammad ticket tab | Chrome | previous Chrome tab |
| shift+ctrl+t | inline translations | Chrome | reopen most recently closed tab/window |
| shift+ctrl+{left,right} [2] | navigate through articles | n/a | nothing |
| ctrl+alt+{left,right} | navigate through articles | Ubuntu | switch workspaces |
- This one doesn’t even make any sense
- Wrong both in the documentation and in Zammads keyboard shortcut list, it’s actually ctrl+alt+{left,right}. See the line below.