user11267: I want to trim a composition b/w the two Composition marker (1) and Composition marker (2):

You see there are many layers with different key frames and I want to trim everything which lies in the selection area. So the rest of the part of the composition (left and right of the two Composition marker (1) and Composition marker (2)) combines and becomes a complete composition.

user11271: As Alex suggested, precomping is the answer to your question. There is no other way to have two separate compositions within one composition. Precomping is a normal part of the After Effects workflow, and is in fact necessary for many effects to work properly with nested elements.
It need not be messy – just organize your project well and label everything clearly. Learning to navigate between your comps with the Tab key will help you to use this workflow efficiently.

11267: <p>I want to trim a composition b/w the two <em>Composition marker (1)</em> and <em>Composition marker (2)</em>:</p>

<p><img src="https://i.stack.imgur.com/rQa5p.png" alt="After Effects screenshot"></p>

<p>You see there are many layers with different key frames and I want to trim everything which lies in the selection area. So the rest of the part of the composition (left and right of the two <em>Composition marker (1)</em> and <em>Composition marker (2)</em>) combines and becomes a complete composition.</p>
 11271: <p>As Alex suggested, <em>precomping</em> is the answer to your question. There is no other way to have two separate compositions within one composition. Precomping is a normal part of the After Effects workflow, and is in fact necessary for many effects to work properly with nested elements.</p>

<p>It need not be messy – just organize your project well and label everything clearly. Learning to navigate between your <em>comps</em> with the <kbd>Tab</kbd> key will help you to use this workflow efficiently.</p>
