I see you already got some options, but I wanted to add the method I use.
Press CTRL + SHIFT + p
Write 'view terminal'
Command palette should now show: View: Toggle Integrated Terminal
Now you can use CTRL + SHIFT + p followed by ENTER to toggle between terminal and the text editor as long as that command is the last used in the command palette.
This option will hide the terminal when you go back to the editor.
An alternative that only shifts focus and keeps terminal visible is here:
View: Focus First Editor Group
Terminal: Focus Terminal
Also found in the command palette.
I know they are not direct shortcuts, but I find the command palette easy to work with, since I have the commands I often use a few clicks away by using the down arrow.