Just like the way the tools hide with "T" or the "N" for the propeties. I know ctrl+space hides everything but the the one your cursor is, but sometimes i need to unhide just a especific tab. Thanks in advance for your help.
The blender opens with the Layout Tab as default. I think you are in the Layout Tab and there is a timeline of course. If you go to the Modeling Tab you will see that there are no timeline there.
This is the Layout Tab with timeline:
And this is the Modeling Tab without timeline:
The Timeline is not part of the 3D Viewport, but it is a Editor Type with a window of its own. In the default start up file you can get rid of it by clicking on a bottom corner of the 3D Viewport and hold and drag it down over the Timeline. (Alternatively you could also right click on the edge of two windows an select Join Areas)
Click and drag the corner back up to make the window appear again. Only now the window is another 3D Viewport so you'll have to change the Editor Type back to Timeline. This for instance can be done to mouse-over a window and press (by default) Shift-F12 twice.
I'm not aware of any quicker way to do this : )
You both are right, there are tabs where the timeline is not necessary and is not part of the 3D viewport. i found and addon where you can open it like a floating window: https://www.youtube.com/watch?v=RyOX8uB_HtQ