Could you please explain the mechanics?
I want to share a folder to an App.
Where and how to do that?
Within DTTG?
Within the Files App?
Or are folders not possible and this only works for single files?
I totally have no idea how and where to do this 
Going to search the PDF, but not sure for what term i need to search
You cannot share groups (folders) but only documents. Groups in DEVONthink To Go are no ārealā file system constructs but virtual, and virtual folders cannot be opened using the Open Inā¦ mechanism. You can, of course, also access everything in DEVONthink To Go through the Files app or any app that uses the file provider mechanism.
So in iOS 13 Files App API changes, it is possible to make it so other apps can ask for access to an entire folder. Secure shellfish supports it and itās pulling files from my servers so I assume that DEVONthink should be able to do it as well.
Only thing is that all of the features that Apple added to iOS that let DEVONthink be DEVONthink require iOS 13/14
Source: ( Whatās New in File Management and Quick Look - WWDC19 - Videos - Apple Developer )
Thatās correct. Unfortunately, DEVONthink To Go doesnāt store its data in folders that closely resemble the file structure you see in its interface. And Apple added these API changes in the most primitive way and completely ignored virtual file systems based on file providers (like DEVONthink To Go and other apps).
You can probably mirror the DB with empty files and folders like the shellfish dev did and load the files on demand but then you would need to have a cache that will take up more space and this would probably be a big task to get files to be happy with loading folders with thousands of files.
Itās doable but no small task. Can be probably considered a major complex feature.
Yes, weād basically need to recreate the whole group structure including replicants in a folder that is then accessible through Appleās mechanism. Unless Apple adds file provider support to their API which opens the feature to all file-provider-based apps in one go. Itās our to-do list.
Ahhh I now understand why DTTG file provider is greyed out in some apps. Thanks for the clarification.
Hi - what is meant by ālong-pressā and which is the option that allows the document to be opened in a PDF viewer? I am not getting a separate menu of options when I select it and Iām not sure which option to use to avoid having the document leave Devonthink when I highlight it. First time user and would greatly appreciate a link to a step-by-step explanation of how to open from DDTG into PDF viewer on ipad!! Thank you!
Use your favourite search engine on āios longpressā for lots of info on this standard Apple IOS feature.
Thank you - I am using the ālong press,ā but Iām just getting the same menu options as regular press - āopen in new window,ā ācopy item link,ā āimport to acrobatā etc - is it one of these commands? The conversation above implies that an āopen inā or āopen withā option should differently show upon long press! Thanks for helping to clarify!
Sorry, I canāt help you. Not only do I not see what you report, but when I ālong pressā a test markdown file I see on an iPhone (fully patched with newest version of DEVONthink ToGo) whatās shown here. Apple IOS must have done something to your setup.
Thanks - thatās helpful to see - Iāll give them a call
You need to share the file first and then long-press the Devonthink icon from the share sheet.
Just found this (for me) very relevant thread. Thanks for the good insights.
Being a DT(TG) user for not too long Iām starting to put office docs in the system, instead of ājustā PDFs for reference.
The process of editing a file within an external app appears different to me than suggested before. (Not sure if that changed but for DTTG 3.5 I found the following working.)
Changes in the file will be reflected in the system. 
