My Thunderbird window is not full screen but it's larger than the mail composition one. I can use that extra screen space to look at other things while I write

My Thunderbird window is not full screen but it's larger than the mail composition one. I can use that extra screen space to look at other things while I write a message. Short messages go through WhatsApp and Telegram nowadays. Outbound email is for important matters, so it's not uncommon to look at reference material. A tab wouldn't do. Inbound email is 99.9% notifications. I read and delete most of them with K9 on my phone before downloading what's left with Thunderbird. BTW my mailbox is on a POP3 server. I clear it after downloading the messages.