nothing to be seen there, answering my question.
Or, what can I be overlooking?
"To expand the work area to the size of the composition, double-click the center of the work area bar."
Double click the center of the work area or. . .
Select the timeline. Make sure no layers are selected and press cmnd/ctrl + alt/option + b.
To set the work area to selected layers select the layers you want to include in the work area and use the same shortcut: ctrl/cmnd + alt/option + b.
Other ways to do this: Press the alt/option + ctrl/cmnd + left arrow to move to the start of the timeline then press the B key. Now press ctrl/cmnd + alt/option + right arrow to move to the end of the timeline and press the B key. This trick will move to the start and end of the layer if you hold down the shift key. If you have a bunch of layers in the comp you can move to the start frame of each layer in turn by repeatedly holding down the shift key. Having a layer selected will not limit the jump to just that layer. If you use the I and O key to go to the in and out point of a layer be aware that the 0 key will take you to the last frame of the layer, not the end of the layer.
To find more Keyboard shortcuts type keyboard shortcuts in the Search Help field in the top right corner of AE or go here: After Effects Help | Keyboard shortcuts reference
Oh my.. I must be terrible at explaining what I want. I do appreciate your help, your suggestions in all about changing the work area, which I do not want to.
I will try here again:
I have a composition of 2500 frames.
I adjust the work area, setting the beginning frame to 126, and the end frame to 226. Ok? Under no circumstances I want to alter the work area's frames span of 100 frames. Your suggestions are about changing the work area's span width. But I want it to remain 100 frames.
My problem is that this work area now obviously is very narrow, so I want to zoom in on this.
The question goes like this, as in my initial post:
What is a fast way to make the work area fill the timeline real estate, without changing its frame span.
I can do this in a very fiddly, cumbersome way, by altering the zoom level and / or dragging the handles of the navigator panel on the of the timeline. What I am after, and have not found, is a way to do this using a shortcut key / clicking somewhere.
Ah, I think that I understand now. You want to zoom in time such that the span shown is just the work area duration. There is no shortcut for that.