Is there a way to limit the targets that are offered for org-refile to the currently visible sub-tree in a buffer that has been created with org-tree-to-indirect or org-narrow-to-subtree
The goal is to make re-organizing entries easier in a file with several large sub-trees.
I don't believe this is possible, alas. Setting org-refile-targets to something like ((nil . (:maxlevel . 5))) will make sure you're only offered targets from the original buffer, but both the indirect buffer and the narrowed view source their completion headings from the source buffer, alas.
If you haven't already changed the value of org-refile-targets, then the configuration I mention above will be very much like the default of ((nil . (:level . 1))).
My best suggestion, frankly, is helm -- perhaps you are already using it? With helm fuzzy-matching, I find it very fast to narrow my subtree selection to a given path, even with a large number of large subtrees available.
org-refile using org-completion-use-ido. Do you know if Helm work fundamentally different for that purpose?