Gmail’s compose feature opens a small window in the lower right corner of the screen for new messages, which can feel restrictive. To expand this window for a more comfortable composing experience, follow these steps:
Start a New Message: Click on "Compose" to open a new message window (you don't have to send it).
Access More Options: Click on the triple dot 'More' icon at the bottom of the compose window.
Set Full-Screen Default: Select "Default to full screen."
From now on, all new messages will open in a larger window, providing more space for composing your emails.