Since you mentioned that you are using a custom UI, the appearance of the in-meeting UI is not controlled by the SDK. As a result, this is not something that we can assist with as you are solely responsible for maintaining the UI of your app. If there is anything directly related to SDK usage in your app that you would like help with, please let me know and I will be more than happy to help.
If you are asking about the default meeting UI, this cannot be modified.
Since you mentioned that you are using a custom meeting UI, you are able to change any UI defined in your app as you please. Enabling a custom meeting UI means that you are telling the SDK you will handle 100% of the UI.