When feed tracking is enabled for cases or work orders, the page-level action menu on those records contains only custom buttons and supported standard buttons. Quick actions appear on the Chatter tab.
Check the below link for more information
https://help.salesforce.com/articleView?id=actions_in_lex.htm&type=5
Sample for Case Object when Feed Tracking is Enabled:
Quick Action:
![](https://www.infallibletechie.com/wp-content/uploads/2018/12/Case2BQuick2BAction2BFeed2BTracking.png)
Page Layout:
![](https://www.infallibletechie.com/wp-content/uploads/2018/12/Case2BPage2BLayout2BFeed2BTracking.png)
Case Quick Action with Chatter Publisher:
![](https://www.infallibletechie.com/wp-content/uploads/2018/12/Case2BQuick2BAction2Bwhen2BFeed2BTracking2BEnabled.png)