Blocks in VEXcode EXP can be deleted in a number of ways.
Drag to Delete
Select a block or a stack of blocks in the Workspace and drag them left to the Toolbox to delete from your project.
Delete a Single Block from a Stack
To remove a single block from a stack, context-select (right click or long press) a block in a stack and then choose 'Delete Block' from the context menu. This will also delete any nested blocks if a block with parameters is chosen to be deleted.
Delete All Blocks
To remove all of the blocks in the Workspace, context-select (right click or long press) the background of the Workspace and choose 'Delete X Blocks.'