Titlebar buttons are great, but since there are so many useful features, you probably end up with a lot of them, what makes the Titlebars cluttered. The buttons overlap the titlebar text or - for smaller windows - reach out of the window.
This could be improved greatly with an additional setting:
Grouped expand/collapse.
An option to create a group of Titlebar buttons that are shown as a single button. Clicking it will expand the group.
This would enable you to have your most used buttons availabe all the time and your not so often used buttons still available, with just one click inbetween. While using up as little space as possible.
This could be further improved by having multiple groups.
Like one group that contains all three mirror-modes, one group for your audio device buttons, one group for your window/position related buttons, etc.
But multiple groups would require an additional set of icons for matching the group... What would complicate the feature considerably.
So, I would be totally happy with a single group option. (just an arrow to expand it)
Important - I don't mean a general collapse/expand button for *all* the Titlebar buttons, (like in Actual Window Manager) but for a specified group of buttons. You should still be able to have your selection of single buttons in addition, that are shown all the time.
About the implementation:
I think expanding the group to the left within the Titlebar wouldn't be the best idea. The icons would probably reach out of the window oftenly.
(if the group is rather large and the window rather small)
One option would be to force the position of the group button to the rightmost position, so that you have the most available space when the group expands to the left. This would overlap the other buttons though, which wouldn't look very good unless the expanded icons have their own background.
So, since you need a background anyway, I think the best option would be to expand them downwards with a background that matches the color of the Titlebar. Either as a vertical stripe or as a small box. Maybe this could be choosable. (expand inside Titlebar / expand downwards)
This would be especially the proper option if you choose to implement multiple groups. So you can place the group buttons wherever you like on the Titlebar, without having to worry about putting smaller groups to the left and larger groups to the right, to have enough space for them to not expand out of the window.
How it expands downwards could be fully pre-defined, like:
If the group has up to 3 buttons, it expands as a vertical stripe. If it's more than 3, it expands as a square box, that has as many buttons per row to keep a square shape.
Or customizable:
1. Expand as stripe or box? (there should be a maximum for stripe, like 8 or so, because too long stripes are inconvenient to use)
2. Row size setting for the box - from 2 to 6 buttons per row.
3. Background color & tranparency
4. Frame on/off
5. Frame size, color & transparency
6. Drop shadow on/off (maybe...)
I hope you like my suggestion!
I think DisplayFusions's Titlebar buttons are one of the most useful tools for improving the operating convenience with a multimedia/multi-purpose computer.