A new button has been added to the textivate front page / editor screen: "Extra gap-fill" (see image below):
This allows you to create an extra gap-fill exercise (funnily enough) based on your own gaps, in addition to the automatically generated one. If you click this button you are presented with a screen on which you can toggle gapped words simply by clicking them.
See an example below:
If you look at the first image above, you'll see that there are lots of [#] symbols throughout the text. These represent the user-defined gaps and ONLY appear on the editor screen.
So you end up with 2 gap-fills.
1. The automatically generated one, which is different every time it loads, and which has the option to increase or decrease the number of gapped words:
2. The user-defined one, which is the same each time as long as you defined 26 gaps or fewer. For more than 26 gaps, textivate randomly selects 26 each time the exercise is displayed:
Hope this is useful.