Mouse wheel tab switching: planned.

Auto promote first child: planned.

Bookmarks sidebar pane: planned.

Better styling of tabs: can you explain?
Auto-collapse unfocused tree: can you explain?

An ability to save both single tabs and branches of tabs to bookmarks is definitely planned and I consider it a core feature. The "metadata bookmark" idea is an interesting one; I'll have to give this some consideration. It would definitely be a hack, but it would sure be nice to have those Sidewise-specific states retained. Perhaps it will be a (default off) option that users can turn on if they want to make that trade-off.


Regarding the issue of feature bloat: I agree this is something to be studiously avoided; I can think of numerous examples of once-great lightweight apps that gradually become laden with features that are low-value cruft, and which end up detracting from the performance, usefulness, and clarity-of-vision of the earlier versions.

I have in mind a "core" feature set that will eventually result in a total of about 9 sidebar panes that will come "built in" with a Sidewise install, and I plan to have 4 or 5 of these *at most* turned on by default, along with an ability for the user to control which panes are visible (and their ordering) in the options page. I consider these "built in" panes to be a part of my original vision for Sidewise, together comprising a comprehensive set of sidebar-oriented tools that give great visibility and control over the user's browsing experience. All of these panes will be designed to work together in a holistic manner.

Any additional sidebar panes will likely be made available by installing extra "sidebar pane" extensions from the Chrome Web Store, which will also allow for other folks to create their own sidebar panes, or give existing extensions the ability to show up as a Sidewise pane.

I am taking a similar tack with the options page, with an overall goal of the default "non advanced" options page taking up about one screen-height at the most. Power users can then "reveal advanced options" if they really want to get customization-crazy.

1. I believe this is technically possible by publishing a binary-compiled Chrome extension (.crx) file and/or creating an NPAPI plugin (like Flash, Java, etc.) Unfortunately, both methods would require a separate means of installation than from the Chrome Web Store, and Chrome team has intentionally made doing this more difficult to do in the more recent Chrome versions. Also, it would be a pretty significant amount of work for this feature, and would only benefit Windows users. So at present I am waiting for Chrome team to implement a proper sidebar API; they had one about 80% complete earlier this year but then decided to scrap it entirely :( and do not appear to have plans to add it back through 2013 at least. I may go this route eventually, but only if Chrome team takes a real long time to give us a proper sidebar API; there are many other features I think would be more useful overall to focus on for now.

2. Interesting idea, I'll definitely consider it. 

Cool got it.

#1: Unfortunately to my knowledge, there is no way to prevent Chrome from doing this. Sidewise creates a new Chrome window to put the sidebar in and as far as I can tell Chrome gives us no control over specifics such as taskbar button. The real fix is for Chrome team to implement a proper sidebar API that extensions can use.

#2: Planned.

Awesome idea. Adding to the todo list.

I've been thinking about making a development branch version available for those who want to try new features before they're fully tested. I'll send you a note if/when I do this.