I'm using Twine 2.0 and Harlowe.
In my game the character "downloads" a link onto their tablet giving them diagnostic information. I was wondering how to write text or better yet make a new link appear on the tablet by the user clicking a button within the passage they're on.
You can use a story variable to track if the 'diagnostic information link' has been downloaded, and then use an (if:) macro to control what is shown to the Reader.
To handle the 'make a new link appear' part of your question you can use a named hook combined with (replace: ) macro, which can be activated via a (link:) macro.
1. Initialising you story variable in a startup tagged special Passage.
2. Conditionally offering a Download option. NOTES:
a. The passage content above the (if:) macro can safely be deleted, as its only there for testing purposes and not needed by the solution.
b. There is a single (white) space character between the opening double open square brackets of the markup-based links and the macro's associated hook's single open square bracket that the markup link is contained in. This is required due to a bug in Twine 2's "Auto create missing Passages" feature.