What's the benefit of such a marker that one cannot recognize without a magnifying glass?
In the original (native) theme, the separators are also barely visible.
Separators should not be clearly visible, because the are not as important as the text of its panels.
I'll add, it's not difficult. Butwe will have to collect all these values and create a centralized palette. the fewer digital values used, the better
IMO the centralized palette is a must-have — it will simplify the development.
If we talk about the colors palette, I strongly suggest to use only custom colors, without asking the system for them. Just define an array with colors, fill them with constant values (using
RGBToColor function) and use everywhere in the package source code. This will allow the IDE to look the same in every user's environment.