Hey Cameron. Here's another vote for PDF. With regards to additional applications I can strongly recommend adding as a first-class use case electronics design where summoning, displaying, comparing and extracting data from electronic parts datasheets is a huge part of workflow. Specific parts of these documents are typically the focus - eg. schematics, physical package drawings, tables. Adding a local (non-cloud) feature to auto-identify or quick scroll-through those to show them larger without manual zoom/repositioning as per current PDF viewer workflows would win many loyal users and should be feasible to build based upon open source OCR layout analysis engines such as tesseract. You may also consider for UI/UX purposes creating either voice input datasheet <MPN> and/or a popup search box with bangs: !datasheet <MPN>, !diagram <MPN>...
Have you tried KDE? It has tiling shortcuts (not enabled by default) and an always-on-top feature for windows.
Also, I once set up KDE 4 to put different apps into tabs of a single window. I'm not sure if KDE 5 can still do that, but it sounds like something that you would be interested in.
You're going to love KDE 5, if your last experience with KDE was back in the early 4 days when it was a memory and CPU hog. Today I don't even notice it at all. Just be sure to disable the File Search feature in System Settings. And it really is called File Search now, not some cryptic name that changed every other version.
Bonsai browser looks great! Especially Spatial Organization.
Is it possible to have nested subfolders?
This could be for browsers (tabs in [project] in [work]). Also in spreadsheets (Excel Sheets inside folders - anyone from Microsoft here?). Also in music (iTunes has playlist folders!). Also in Contacts (people in [social group] in [country]).
The way I imagine the user interface is similar to existing tabs or bookmarks, but with a drop-down menu, and to be able to easily access all sub-items by clicking the folder.
