You would expect to have some UI button in Skype to add more Moderators to your group. But only the Creator/Moderator can remove them. You may want to remove members when it's time to do so.

People move on and there's always the possibility the originator of a group will hand the baton over to his/her successor, For whatever reason To ensure you’ve selected the correct audio device, open Skype, tap the three dots next to your profile name and click Settings.Sometimes one person creates a group (and becomes the Moderator), but other people are really running the group. If you’re using a wireless microphone or headphones, ensure they’re fully charged, and use the physical mute buttons on them to check if either device is muted or not.Check whether your internet connection is working as this could prevent you from receiving good audio during a video or voice call.If you knowingly or unknowingly installed such a program, check installed software and uninstall or disable the program.

Some programs can prevent your microphone from working and you end up with no sound on Skype.

Check whether the audio in Skype is muted by looking at the microphone icon and checking if it has a diagonal slash across it.

Use a different pair of headphones or microphone.

Check that you’re using the device selected in your Skype sound settings if you have multiple devices listed.

To do this, open Control Panel> Sound (or Sounds and Audio Devices), and ensure the sound devices match. For Windows PCs, compare the sound settings with the Skype Audio settings.Install device drivers for audio USB devices like your headphones or microphone, and then re-launch Skype.If you’re using headphones or a microphone, make sure the jack is properly plugged into the right audio input and output ports on your device.Try the following techniques to resolve sound issues on Skype before moving to other advanced solutions:

How to mute a chat on web skype