Yes, we're seeing the same behavior after upgrading to Zoom Workplace 7.0.5. The pop-out chat option disappeared from both the right-click menu and the in-chat menu, and it does not return after restarting the application.
From what I've found, this appears to be related to Zoom's new Chat experience introduced in version 7.0.5. Zoom's documentation notes that the ability to pop out chat windows "will be introduced soon," which suggests the feature may have been temporarily removed or is not yet supported in the new interface.
You're definitely not alone—other users have reported the same issue since updating to 7.0.5 and are hoping Zoom restores the functionality in a future release.