Note: As of July 9, 2018, Blackbaud’s School Management solutions (which include Core,  onBoard, onCampus, onMessage, and onRecord) are utilizing a new top level navigation. This primarily affects users performing administrative tasks—constituent navigation for most parents, students, faculty, and alumni will remain the same.   
We appreciate your patience as we work to update our documentation. If you are seeing this message, the content of this solution is still being vetted for possible updates. Please refer to this mapping document if you need assistance finding a task in the new navigation.  

It is possible to inactivate a Block however the Block will still show up in the Block dropdown menu. You can click Edit Order and Drag the Active Blocks to the Top. There is an idea in the Ideas Portal for this which can be found at: 
 https://blackbaudk12.ideas.aha.io/ideas/K12CO-I-1406