I agree with @TDK_SA90 that for something like this you might well be better off looking at how to simplify the interaction and get it directly into somewhere you might use it; thus addressing the need to import, though that could potentially be automated depending upon your avalable resources.
Here’s one for use with Dropbox as per your scenario.
let fmDropbox = Dropbox.create();
let strFileContent = fmDropbox.read(p_strFilePath);
//If the file does not exist write the draft content, otherwise combine and overwrite
if (strFileContent === undefined)
fmDropbox.write(p_strFilePath, draft.content, "add", false);
fmDropbox.write(p_strFilePath, strFileContent + draft.content, "overwrite", false);
Here’s another one for use with iCloud.
let fmCloud = FileManager.createCloud();
fmCloud.write(p_strFilePath, fmCloud.read(p_strFilePath) + draft.content);
You can adopt similar approaches for other cloud storage providers compatible with Drafts.
Hope that helps.