... too often, with the triangles, they were made equilateral, so it was never clear from just looking at them whether or not they were collapsed or expanded.
Interesting. Similar to the "confusion" I experience with the single-state downward chevron "V" often found in MC Options submenus. That's what launched me on this quest for an alternative. The 3-bar menu symbol resolves it with a clean contemporary look. However, some may consider it a little heavy-handed for this application. After all, these are really drop-down menus, not "full fledged" independent popup menus or screens. With this in mind, the filled right chevron is attractive, probably because it is simpler and I am so conditioned to expect it to open a submenu to the right. At least JRiver makes it relatively easy to try both, choose whatever floats your boat, and change it if you get bored.
One might expect that the filled downward chevron, usually found in a selected view tab, would be confusing for the same reasons as the "V". Except the drop-down menu appears immediately with a mouseover, and there are no closely adjacent copies of the same static symbol, which together effectively resolve it for me in the view tab.
Re circles for the top level tree branch expansion - never saw your old posts in this regard, but I agree with you - immediate fast visual information, no thinking about right v.s. down pointers is required! Though like most symbology, even circles take a little learning, especially because they are not "hinted" like arrowheads. As you might guess by now, I am always on the lookout for minimalist solutions! However, enhancement here at the Tree's top level with a gentle 3-state response would be nice to try (especially since it is also used in the main window Tree panel). I hope it could be made backward compatible with existing 2-state treatments as long as the
NumberImages parameter agrees with the artwork.