> I guess it's hard for me to edit things that I don't see right in front of me or aren't super simple changes (like name changes). Or at least, basic things I can reason about (such as finding by regex then deleting by textobject or something).

This is actually what's nice about tools like ast-grep. The pattern language reads almost like the code itself so you can see the transformation right in front of you (at least for small-scale cases) and reason about it. TypeScript examples:

  # convert guard clauses to optional chaining
  ast-grep -pattern '$A && $A.$B' --rewrite '$A?.$B' -lang ts

  # convert self-assignment to nullish coalescing assignment
  ast-grep -pattern '$X = $X ?? $Y' --rewrite '$X ??= $Y' -l ts

  # convert arrow functions to function declarations (need separate patterns for async & for return-type-annotated though)
  ast-grep -pattern 'const $NAME = ($$$PARAMS) => { $$$BODY }' --rewrite 'function $NAME($$$PARAMS) { $$$BODY }' -l ts

  # convert indexOf checks to .includes()
  ast-grep -pattern '$A.indexOf($B) !== -1' --rewrite '$A.includes($B)' -l ts

The $X, $A etc. are metavariables that match any AST node and if the same metavariable appears twice (e.g. $X = $X ?? $Y), it requires both occurrences to bind to the same code so `x = x ?? y` will match but `x = y ?? z` won't. You can do way more sophisticated stuff via yaml rules but those are less visually intuitive.

Sadly coding agents are still pretty bad at writing ast-grep patterns probably due to sparse training data. Hopefully that improves. The tool itself is solid!