I’d been thinking about this as well! Haven’t brought it up because I appreciate that Drafts != Roam/Obsidian/Logseq, and as @sylumer queried, I do wonder what benefit graphing actually offers.
Exporting hierarchical “trees” of notes to iThoughts is relatively easy to do— I’ve already hacked together a couple of actions based on this notion. You can write markdown links in iThoughts nodes, so it’s again easy to construct tidy links that point back to individual drafts.
I don’t think it’s as easy to graph a visualisation of networked notes rather than branch/tree nodes, however. Cross-links across branches work differently than regular child-parent connections. Even if there’s a way of communicating the necessary information from Drafts (how a note links to other notes, beyond a hierarchy of indents), iThoughts currently doesn’t render those kinds of links particularly well— for example, cross-branch links have to be manually arranged so as not to cross through nodes.
With that, and the fact that the map you create when you move from Drafts to iThoughts isn’t “live”— I’ve ended up not making much use of the actions I’ve already experimented with.
After thinking further, I arrived at the conclusion that visualising the already hardwired links between documents probably wasn’t all that meaningful for me— what I might actually be thinking about is some way of doing this: https://noduslabs.com/cases/evernote-iphone-notes-text-network-graph/— and that the graphed visualisation is nice to look at, but that what it actually facilitates is foregrounding unexpected connections (rather than the connections that already exist). Still dreaming in this direction…
Another way to think about this: for a while I was using an iThoughts map to serve as a top-level overview for themes/topics/subjects in my notes. Terminal nodes in that map either link to specific drafts or to keywords for a Drafts search action. I think this might be akin to Zettelkasten’s “structure notes“?