Glad to hear that it's sorted. Let me know if there's an issue with one of the Windhawk mods.

Is it related to the start button issue, or to 7+ Taskbar Tweaker at all? Please provide more details or create a new ticket if it's an unrelated issue.

Are you using Windows 10 or Windows 11? Also, please post a screenshot to show how it looks for you.

Edit: I just tested this on an up-to-date Win10 build (19045.5679) and it works as expected for me with multiple monitors.

The “Open With” feature is a built-in feature of Windows, not a feature that the tweaker adds. You can activate it by holding the Shift button. All that the tweaker does is making Windows think that you’re holding the button.

The "Middle click to mute" option requires Windows 11 version 22H2 or newer, and isn't supported for the old taskbar if a tool such as ExplorerPatcher or StartAllBack are used. If you think it should work, please create an issue here:
https://github.com/ramensoftware/windhawk-mods/issues

Regarding the "especially" word you used, what other issues are there? Please report any issue on GitHub with the relevant details.

Which version of StartAllBack is being used? Versions 3.8 and newer aren't supported, see:
https://tweaker.userecho.com/topics/1307-7-taskbar-tweaker-isnt-compatible-with-startallback-38

The solution for error 102 is to reinstall the tweaker, as the error message says. Please reinstall and let me know if the error persists.

Sure, a solution would be something along those lines, but there are several unknown variables, including when exactly to apply the new width, and how it's represented (e.g. in case of monitors with different scale settings). It was reported that restarting the tweaker doesn't make the taskbar narrow again, while I expected it to work as the last used width is stored in the settings. In short, it requires time and effort which I'm not able to invest currently.

I looked at the log, but it didn't yield the result that I hoped - quickly seeing the reason for the problem and coming up with a fix. Unfortunately, I think the easiest way for me to understand the problem is to get an environment that can be used to reproduce the issue. That requires time, and while I might have a look at at some point, for now it's not planned, sorry.