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Quick Look preview from File Explorer

in 3.7 pre-rel
Select a file in File Explorer (or on the desktop) and press Space to preview it in a popup, like macOS Quick Look. Esc or Space closes the preview, and Left / Right show the previous / next file in the folder. Turn it on with the ExplorerQuickLook advanced setting. The new command-line options -quicklook and -quicklook-agent support this feature (#2568).

Vimium-style keyboard link hints

Shift + F (Follow Link With Keyboard, CmdToggleKeyboardLinkFollowing) now labels the visible links with letter hints, like the Vimium browser extension. Type a hint to follow its link. The labels replace the earlier 1-9 numbers, so you are no longer limited to nine links (#2629).

Uniform Page Width

Uniform Page Width in the View menu (CmdToggleUniformPageWidth) shows pages of different sizes at the same width at percentage zoom levels, using page 1 as the reference. The choice is remembered for each document (#5512).
Pages of different sizes at 20% zoom, without and with Uniform Page Width

Landscape comic pages shown as spreads

In facing and book view, a landscape comic or image page (wider than it is tall) now takes up the whole two-page row, so a double-page spread stored as one image looks like a centerfold. Turn it off with ComicBookUI.LandscapeAsSpread = false or ImageUI.LandscapeAsSpread = false (#1324, #872).
A landscape comic page taking a whole row in book view

Table of contents from numbered headings

If a PDF has no outline, the Bookmarks sidebar can be filled from numbered headings in the text (I. Introduction, 1.2 Title, and so on), so you can jump around papers and reports that never stored a table of contents (#5724). Use Generate Table Of Contents (CmdAutoGenerateTOC) in the command palette, or set AutoGenerateTOC = true to do it whenever a PDF is opened.
Bookmarks sidebar filled from the numbered headings of a PDF without an outline

Follow Windows theme option

The Change Theme dialog has a Follow Windows option. With it on, SumatraPDF switches between light and dark automatically when Windows does (same as Theme = System) (#5995).
The Change Theme dialog with Follow Windows at the top of the list

Favorites remember scroll position

When you jump to a favorite, you now return to where you were scrolled on that page, not just to the top of the page (#4986).

Smooth arrow-key scrolling

When SmoothScroll is on (the default), arrow-key line scrolling now animates smoothly, like mouse-wheel scrolling (#4662).

Altium schematic component popups

Clicking a component in an Altium Designer schematic PDF shows a popup with the part’s properties (comment, footprint, value, and so on). Lines that contain URLs can be opened. These hotspots use Acrobat JavaScript and did nothing before (#1198).
A popup with a component’s properties after clicking it in a schematic PDF

Form-field tooltips

Hovering over a PDF form field now shows its Acrobat tooltip (the /TU text), if the field has one (#2083).
A form field’s tooltip shown on hover

Better reading of manga and fixed-layout books

PDFs that declare right-to-left reading (ViewerPreferences/Direction) now open in right-to-left layout (#2022). Kindle KF8 (AZW3) fixed-layout books now show their image pages (#4315). Very large JPEG images open and render again (#4843).

Page dimensions in points

Document Properties shows page dimensions in points (72 per inch), not in engine pixels (#5992).

OneNote and Outlook PDFs no longer locked

PDFs opened from OneNote or Outlook cache folders are copied before they open, so the original file stays unlocked and OneNote can sync the section (#4705). Comic archives of 32 MB or less on network drives are loaded into memory instead of being copied to a local cache.

Remote Desktop DPI changes

When you connect over Remote Desktop at a different display scale, the toolbar, title bar, bookmarks and menus now resize to the new DPI without a restart (#4581).