If saving is too slow for you in the new SwiftUI DocumentBrowser wrapper, here's a terrible trick to make it instant. (This is new API in iOS 14; Apple might change the underpinnings to not use UIDocument, so this might fail in future updates. InterposeKit fails gracefully and worst case you end up with the save delay). FB8748779

SwiftUIDocumentBrowserSpeedup.swift

    private func speedupDocumentSaving() throws {
        // SwiftUI triggers updateChangeCount: when the binding changes,
        // which triggers an autosave operation to eventually store the document.
        // There's no direct way to access UIDocument (used inside SwiftUI.PlatformDocument)
        // to speed up this process. It is noticable as it delays changing the thumbnail.
        // While saving is triggered instantly when the application backgrounds,
        // we still want to update the document immediately.
        //
        // We could apply this to SwiftUI.PlatformDocument for a more narrow tweak.
        // We could also swizzle the NSTimer initializer, check for the target being PlatformDocument
        // and modify the value there (which would not be private API, still hacky tho)
        _ = try Interpose(UIDocument.self) {
            try $0.hook(
                // This is private API, so we hide the selector.
                NSSelectorFromString("otua_".reversed() + "savingDelay"),
                methodSignature: (@convention(c) (AnyObject, Selector) -> CGFloat).self,
                hookSignature: (@convention(block) (AnyObject) -> CGFloat).self) {
                store in {
                    let originalAutoSaveDelay = store.original($0, store.selector)
                    print("Changing autosave delay from \(originalAutoSaveDelay) to 0")
                    return 0
                }
            }
        }
    }

Swizzling powered by https://interposekit.com/