If I wanted to open a link in my center frame on the middle of the page what would my target frame be called?

There are not frames on the pages. The center content is defined as <-- System:Content --> or something like that in the advanced layout. I don't think there is any way to target that as a destination for custom content.

--
Six Demon Bag
Jack Burton: Hey, what more can a guy ask for?
Egg Shen: Oh, a six-demon bag!
Jack Burton: Terrific, a six-demon bag. Sensational. What's in it, Egg?
Egg Shen: Wind, fire, all that kind of thing!

Are there any future plans to enable the use of the center space for custom content?

You can certainly add your own content. This functionality has been added since this thread was made. Check out Admin > Static Menu Items and Content.

You can define things as a link that opens in a frame, or you can enter your own BBCode text, or your own HTML if you like.

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It's all in the reflexes.

Hmmm. I'm not sure if I can quite do what I want from there. What I am really trying for is the ability to put a custom menu in the large center space instead of on the side.

I'm not sure I'm following, but if you had an example, perhaps I could help to get done what it is you're trying to do.

--
It's all in the reflexes.

So this really isn't that hard. It's similar to what I did with moving the Statistics Frame into the middle of my page. Unless this is a menu you don't want to show up all the time. If you just want a menu in the center column of the page just define it within that Column or Table and place it above or below the System Content and Title tags.

--
Six Demon Bag
Jack Burton: Hey, what more can a guy ask for?
Egg Shen: Oh, a six-demon bag!
Jack Burton: Terrific, a six-demon bag. Sensational. What's in it, Egg?
Egg Shen: Wind, fire, all that kind of thing!

OK, if you go under Admin > Custom Menus you can create a menu for either side in which you can do fun things like run a custom Vent Status script, but they can only be on the left or right, not in the center.

If there is a way to do the same thing under Admin > Static Menu Items and Content, I am not certain how.

Those custom menus can be anywhere you want. You just call them by using the command <!-- System:Menu:CustomMenuTitleHere -->.

You just have to manually edit the HTML of the site yourself. I don't know if you can put the menu in the center using one of the default layouts.