Rated 5 out of 5 stars
Works very nicely! Please consider removing the purple background and custom styling on the sidebar splitter. The default theme and custom themes already have styles for these that you are breaking in a way that may be irreversible.
Tree-Style-Tabs had a nice option where the user could choose between the custom styles and letting the theme do the styling. Many themes are already compatible with vertical tabs!
I appreciate the review. I agree, the ability to inherit styling from your current theme is a good idea. I plan to include that along with additional customization options in a future version of Side Tabs.