Thanks for creating this theme!. I have a proposal regarding the tabs part of the interface. I use the Dark - Medium contrast so the proposed modifications must be tested with this contrast.
// Settings for the theme: Gruvbox Dark Medium
"workbench.colorCustomizations": {
"tab.activeBackground": "#3c3836",
"tab.inactiveBackground": "#282828",
"tab.activeBorder": "#689d6a",
"tab.unfocusedActiveBorder": "#689d6a",
"editorGroupHeader.tabsBackground": "#282828",
"editorGroupHeader.tabsBorder": "#3c3836",
"statusBar.border": "#3c3836",
},
My motivation was that I didn't like that every other element of the interface blends in with the same background color except for the tabs. Also, I added line border (lighter color) to visually differentiate the status bar and the tab bar and an extra highlight in the border of the active tab (focused or not).