Text-to-speech properties can be edited by clicking on the object in the Timeline.

In the Object Inspector, you can rename the object, edit its text.

1. Name
   The default name is 'Text-to-Speech X' ('Text-to-Speech 1', 'Text-to-Speech 2', and so onward), and this is visible in the name property of the object. You can change the name by deleting the default name and typing in another one.
2. Text - Microsoft Speech API
   

   Learn more...

   Use the slider to set the rate value or enter it manually (-10 to 10). Use the slider to set the volume value or enter it manually (0 to 100%). Click Convert to convert the text.

3. Text - Google Cloud Text-To-Speech
   

   Learn more...

   Use the slider to set the rate value or enter it manually (25 to 400%). Use the slider to set the volume gain value or enter it manually (-10 to 10 dB). Click Convert to convert the text. In the Cloud Console, on the project selector page, select or create a Google Cloud project. Make sure that billing is enabled for your Google Cloud project. Enable the Cloud Text-to-Speech API. Click the menu button and select APIs & Services > Credentials. On the Credentials page, click Create credentials > API key. The API key created dialog displays your newly created API key. The new API key is listed on the Credentials page under API keys.   For more details, please follow this link.

4. Volume Control
   

   Learn more...

   Use the slider to set the volume value or enter it manually (0 to 200%). Enter Fade In and Fade Out values to specify the audio transitions (in ms: 0 to 2000).