Dingdong! Dropbox has implemented the fully-featured Files app integration we've all been waiting for.
Previously, Dropbox folders appeared greyed out in file pickers. They had other priorities. With their recent update, they're now fully accessible. Thank you, Dropbox.
This means seamless integration between Dropbox and iA Writer across iOS, iPadOS, macOS and Windows. Time to celebrate! 
iA Writer had Dropbox since V1. When Dropbox discontinued the 2nd API and wanted everyone to create the 3rd client side custom sync, we asked ourselves:
Another buggy API that still required extensive workarounds, maintenance and leads to data loss, we'd get blamed for? No.
About 15% of our users relied on Dropbox. Deciding not to develop our own Dropbox syncing and waiting for them to properly implement it on the OS level was one of the most agonizing decisions we've ever made.
We were never really happy with our decision, because it was a tough often final no to a lot of our earliest and most engaged users. But it was nevertheless the better decision of two unpleasant ones.
What Dropbox now offers is the proper Dropbox and Apple way to do it. Document syncing is not our core competence, it's theirs, and doing it on OS level is their sales proposition, their responsibility and their business.
Now waiting for Google Drive to follow up and do the same. 
@ia this changes everything! W00t. excited how this will break a bunch of workaround I currently use.
Does Dropbox also become a 1st class citizen regarding shortcut integration?
@ia Wait what? What did they change? I thought they already did integrate with Files. Is there a blog post about this or something?
@jsit It's not well documented. There's one rudimentary reply in January 2024 on their forum that talks about it. We discovered the change (that we've expected for years) by chance, yesterday. https://www.dropboxforum.com/t5/Apps-and-Installations/iOS-app-quot-Convert-all-to-classic-integration-quot/m-p/742129
@ia Good news. But, while you’re on the subject of Dropbox (historically) doing things in a non-standard way, any plans to make iAWriter’s file navigation less weird and more standard? (Admit it: it’s a hot mess at the moment. Come on, please, give us standard file-tree navigation!)
@richardcarter @ia and if possible, please introduce sort by date for file on Dropbox in Android App! It's a great mess now, for large directories
@mcastel We've wanted this for a while too. Dropbox API weirdly doesn't offer a method for it: https://www.dropboxforum.com/t5/Discuss-Dropbox-Developer-API/Sorting-Dropbox-Folders-by-Most-Recently-Added-or-Updated-Files/td-p/727577
@ia It’s interesting how some “older” tools used to sync their data or settings via Dropbox (I’m aware of Forklift, for example). Nowadays, you mostly see apps sync their data via iCloud. I definitely welcome this change, as Dropbox (at least their web interface) has gotten quite terrible in the recent years.
@ia @nextcloud and OneDrive, your move please!
It’s a very important feature for iOS users.