How do you reset the layout of AE to the original size (include the size of the windows)?

Use the Window/Workspace/Reset "Your Chosen" Workspace to default values Menu Or simply double click the current workspace in the toolbar and choose Yes. This workspace is about as fouled up as I can make it and it's reset in a couple of seconds.

You should also expand the workspaces in the tool bar and edit the ones that are visible in the tool bar by just dragging them around. Workspaces are a fabulous time saver. This is how mine are setup.

The expressions workspace is a custom workspace I created and saved just for writing expressions.

CTRL + \ or CTRL +ALT + \ should do the trick. These Maximize AE's App Window or displays the entire app window including project path details. HTH

Hi default9vvcyoqmh88r,

Thanks for reaching out.

After Effects's interface is customizable. Here's a YouTube video that should help: https://www.youtube.com/watch?v=BD0USs8oVig&ab_channel=MOBOXGraphics

If you want to reset everything to the default, you can reset the preferences (I don't think it's necessary). Here's how: https://community.adobe.com/t5/after-effects/faq-how-to-reset-trash-preferences-in-after-effects/td-p/10634342 

Let us know if this is not what you're looking for.

Thanks,

Nishu