Yes! You can hide tracks and when you do, your changes are instant. There's no need to send out new email invitations!
To manage track visibility:
1. Hover over Releases and click on My Releases
2. Select a promo from the column on the left side of the page
3. On the right side of the page, scroll down until you see the track list
4. Simply click the switch to toggle between hidden and visible options
*** Hidden tracks are not included in a promo's ZIP download. ***
As an example, here is a full track list in a promo, viewed by one of your contacts.
You decide you don't want to release the entire album quite yet. Going back to your promo editing screen, you switch off every other track.
If you then go back to the promo and refresh the screen, you will see the changes. Keep in mind, hidden tracks will be excluded from the zip download in addition to the track list.