H0i! I’m new to aseprite but I think it’d be nice if this was a thing? Or maybe an extension to change it?
You can change whether Opacity uses 100% or 255 using the Preferences, under the Color tab.
You can also make a custom Brush (Ctrl+B), which does show opacity at the top of the bar. If you make a custom Brush of a single pixel, that should work the same as the default Pencil tool.
Extensions are not currently able to adjust or add things to the toolbars, as far as I’m aware!
Thank you!