Good question. The same question came up during the Early Adopter testing for 4.0:
No bug was ever logged, but perhaps one should be. I will look into this a bit more before logging one.
SQL Developer Team
I found a back-door way to get this functionality back.
The capability wasn't actually removed, the option to set it is no longer available in the IDE interface.
The configuration file for keyboard accelerators is located here:
%USERPROFILE%\Application Data\Sql Developer\system184.108.40.206.48\o.ide.220.127.116.11.41.140207.1351\settings.xml
In the file "settings.xml", make sure this line exists (set the keystroke to your preference, I use shift control T). Also make sure any other accelerator that uses the same keystroke is removed. I had to remove one for "set thumbnails".
<Item class="javax.swing.KeyStroke">shift control T</Item>
With this block of text in my settings.xml file, and every other reference to "shift control T" removed, Sql Developer now behaves the way I want it.