Review the difference between a sequential and parallel project or sub project. That is the level at which you need to deal with this issue, the project level. At least in GTD methodology, if something has more than one step to complete it, then it's a project.
So in your situation, you take the two tasks and you drop them into a sequential project. Then, the second task will not show as available until you have completed the first one. Conversely, if you set the project as parallel, then both tasks will show as available immediately.
Once you understand how this works, you can create some rather intricate chains of dependency.
For example, lets say you have a master project Called Project A and two sub-projects under that heading: Sub-Project 1 and Sub-Project 2. So it looks like this
You have three choices about setting parallel vs. sequential for this set items.
You can set Project A to to parallel or sequential and this will affect what items you see as available from Sub-Project 1 and Sub-Project 2.
You can also set parallel or sequential for each of the two Sub-Projects as well, and this will affect what items you see from those headings.
So if you set Project A to sequential, then you won't see anything as available for Sub-Project 2 until Sub-Project 1 is complete.
But if you set Project A to parallel, then you'll see items from both of the Sub-Projects as available immediately.
Which items you see from each Sub-Project will depend on the sequential/parallel setting for that project.
If you set Project A to sequential and Sub-Project 1 to sequential, then initially you'll see this:
Task 1 of Sub-Project 1.
But if you set Project A to Parallel and both Sub-Project 1 and 2 to parallel, then you'll see all of the tasks from both sub-projects as available immediately.
From there, you can mix and match to get what you need.
It probably doesn't handle every situation perfectly, but once I understood how this works, I was able to accomplish most of what I needed most of the time.