This is more a general hope/suggestion, but it’s one formed haven taken note of general forum feedback over the years.
DEVONthink is a deep and somewhat complex application, one which necessitates a 345-page reference PDF (at latest count, for DEVONthink 4, beta 1).
With this in mind, and at this point in the development lifecycle of DT (an application that’s been around approximately 20 years), I think it could be to the benefit of all, if the core UX/UI was refined to aid function discoverability and to reduce user errors with complex rule based functionality.
The support provided through this forum is amongst the best I’ve witnessed for any macOS application. And the manner in which the in-app documentation is designed is also of a very high standard. But I do think both the UI and UX could benefit with being more intuitive, even for technical users. As an example, some of the best features of DEVONthink aren’t easily discovered, especially with the sheer amount of functionality one accesses via the Inspectors on the right side of the UI.
I make it a habit to go through the entire PDF reference documentation of my mission-critical apps when major revisions occur. But let’s face it, not many people do this. It’s great that you use Google Gemini Flash for in-app documentation search, as I think this provides a looser, more intuitive way to locate relevant information in the documentation. But I believe rich pop-over tooltips within the application forms themselves are an even better place to provide entry points to relevant sections of the in-app documentation. And those tooltips could provide more guidance in and of themselves (meaning the user doesn’t feel the need to read the documentation). A prime example is the SmartGroup/Rule forms. The only tooltip in this section is the technical describer “Option Click + to create compound predicates”. Great for informed users, but less helpful for those looking for guidance with the variety of form options.
Another area which could be improved is the document viewing options. Whilst it’s great that individual documents can be opened in new tabs, a more valuable option, would be the ability to open multiple document views beside each other, much as one can in Obsidian (via ‘Split Right’, ‘Split Down’), Scrivener (‘Split Horizontally’, ‘Split Vertically’) and Ulysses (‘Open in Second Editor’). The closest DT gets is the option to open documents in a new window, which isn’t the same as viewing unobscured documents beside each other (a very useful technique when writing new original content, based on other existing reference documents).
But as I said at the outset. These are only suggestions. DEVONthink is one of those applications that takes time to use effectively. The biggest challenge for the DT team (IMO), is to help customers discover the user journeys that best suits their individual needs. It’s a common problem for mature applications that empower users in such a wide variety of scenarios, and the answer to this challenge most often involves a renewed focus on the overall application UX/UI conventions.