best organizer(moderator) to presenter(speaker) to organizer transition

Hi zitrola welcome to the Community, 

• First I highly recommend using  Practice mode before the webinar, where Co-organizers and panelists can join the practice session as they would the regularly scheduled webinar by selecting the join link in the confirmation email. This will help all involved feel more secure before the big day. 
• When you start the webinar you will be in pre-broadcast mode. You and other staff members can communicate privately until you're ready to start the broadcast. You microphone is on if the icon is green and your camera is off if the camera icon is grey. You can hover over both icons to be sure.
• To Share Your Screen, click Sharing and Show Screen  Select the screen or application you want to share
• When you're ready, select the "Start Broadcast" option from the webinar's control panel. This will allow attendees to hear your audio and see your shared screen.
•  After your introduction, you can enable the audio and video of the panelist by clicking on Attendees, under Staff,  you will see a Microphone and Camera Icon, press both to green. 
•  Once the panelist is done, you can disable their video while keeping their audio on. Then, you can re-enable your audio and share your screen again.
• Check out this article on how to use the control panel for more information. 

Note that this image is for the classic GoTo Webinar, not the new beta experience.