You're using the beta version. Some features are not always available in beta versions. For day-to-day use, I suggest using the release version instead, which is 102.10.1

Updated to version 113.0b4 (32-bit) What happened to a display of the size of fodlers in the Folder Pane? I miss it!! george Albuquerque, NM online@pngyoung.com

Message counts have returned. I doubt folder size will, but you can see it with right+click > properties.

https://thunderbird.topicbox.com/groups/beta for more information