Just added a backup battery WB37 to my RC Plus controller. Shouldn't I see a charge status here?

Hi, there. Sorry for the belated reply.
1. You are currently inserting the WB37 battery and not charging the built-in battery because the built-in battery of the remote control is at 100%. You can refer to the icon on the left of the location you marked.
2. When the external battery is used to charge the built-in battery of the remote control, the charging icon will be similar to that of a mobile phone connected to a charger, which can be viewed on the main interface of the remote control.Hope this helps.
Thanks again for your support.