I've got a task group

      <task name="Create ASPX Detail Pages" assemblyFilename="SD.LLBLGen.Pro.LptParser.dll" taskPerformerClass="SD.LLBLGen.Pro.LptParser.DotNetTemplateEngine">
        <parameter name="destinationFolder" value="Home"/>
        <parameter name="filenameFormat" value="[elementName]Detail.aspx"/>
        <parameter name="templateID" value="OMP_DetailASPX"/>
        <parameter name="emitType" value="allEntities"/>
      </task>

and I want to exclude a specific entity from it. Is this possible? I've looked for ways to do this in template code like SuppressOutput property or something but I can't find anything.

Ideally after i hit F7 I could hit "View task details" and expand that task and exclude entities from being used by that task.

Do you mean specific entities or all entities?

Only when you select a set of entities to participate in the generation run. Though that thus means the entities not in that set will be excluded for all tasks.