The “New Tab” menu item has been removed from GNOME Terminal, and instead there is only a single “Open Terminal” option.
This option will open a “New Window” or a “New Tab” according to the preference we have set.
So depending the Terminal preferences, we will have the corresponding behaviour.
The Tricky Part
GNOME seems to love key modifiers. <Ctrl+Click> will modify the option to the opposite.
If we have set “Open Terminal” to always open a “New Window, by pressing <Ctrl+Click> we will launch a “New Tab”, and vice versa. This change is documented in help.
Once you have set the preference, you can use <Ctrl> to invert the preference. For example, if you have your preferences set to open a new terminal in a new tab, then pressing “New Terminal” will open a new tab.
On the other hand, if you hold down <Ctrl> and then press “New Terminal”, then a new window will be opened instead.
By the way we can open a new tab with <Shift+Ctrl+T> and the more meaningful <Ctrl+T> doesn’t work because it is a Bash Keyboard Shortcut. That has been changed in gEdit 3.12 and <Ctrl+T> now opens a new tab.
From the bug report: #543996
Window: Unify new tab and new window
Instead of having two sets of “New terminal” items, unify them into one “New Terminal” type of items that will open a terminal in a tab or window depending on a pref, and that can be inverted by using control key.
The patch is kinda old (Jun 21, 2013), but it seems that just now (3.12) arrived. At least in Fedora.