Just to complement @FlohGro’s example, here’s the other way of doing it I suggested.
This action has two steps. The first is the script step that stores the content of the, for want of a better term, ‘special’ draft, in a tag associated with the current draft. For your circumstances this would be your to do draft.
//Change the UUID in the find parameter below to be your own draft
Simply substitute in your UUID for the one I used for my test.
Note the tag being created is called “SpecialContent”.
The second step is a standard preview step, but I swapped out the
%%[[draft]]%% tag for
This doesn’t load the draft into the editor, so if preview rather than edit is preferred then this would be a better option. If you want to load the draft too, then the previous solution would be appropriate.
Whilst you could of course add a load step as a third step in this action, thus keeping it all in one action, if you have tailored styling for the preview and wish to re-use it across multiple similar actions, then the previous solution where it splits the actions would be more efficient overall as you could retain a single style source.
There are other ways to do that, but it would be the easiest to maintain.
Hope that helps.