Gmail app > allow "popouts"?

Wondering if anyone knows for a way to allow popouts when using the Gmail app? For example, when I try and start a new message in a “popout” in Gmail (on the Mac, clicking “Compose” while holding down the Command key would open a “new message” in a new tab, when using Chrome).

When I do this in the Gmail app, I get the following notification:

Grrr! A popup blocker may be preventing the application from opening the page. If you have a popup blocker, try disabling it to open the window.

Hoping there might be a way to allow this?

Thanks,
Kristin.