Track View > Global Tracks > Block Control > Click and then right-click MasterBlock track. > Properties > Master Block Parameters dialog > Add > Track View Pick dialog
This dialog is displayed when track selection is necessary, by clicking Add in the Master Block Parameters dialog, for example. Select tracks in the dialog that you want to include in a Block. Valid tracks are darker.

Cancel—Exits the Track View Pick dialog with no changes.
If tracks are highlighted in the Hierarchy list, then the Block Parameters dialog is displayed when you click OK, to allow you to set the duration for the Block.