You might find this workaround useful:
- Close Zotero.
- Open your Zotero profile folder.
- Inside this folder, create a sub-folder named
chrome
.
- Inside the folder
chrome
, create a file named userChrome.css
with the content below.
- Save. Reopen Zotero and enjoy.
Tested on Linux Mint 21.2 with the default dark theme.

.tabs::before,
.tabs::after {
border-color: var(--tabs-border-color, rgba(0,0,0,.3)) !important;
}
.tab {
background: inherit !important;
color: inherit !important;
}
#tab-bar-container .tab:not(:last-child) {
border-color: var(--tabs-border-color, rgba(0,0,0,.3)) !important;
}
#tab-bar-container .tab.selected {
background: inherit !important;
border-color: var(--tabs-border-color, rgba(0,0,0,.3)) !important;
border-top-color: var(--tabline-color, #0a84ff) !important;
}
#tab-bar-container .tab:not(.selected) {
border-bottom-color: var(--tabs-border-color, rgba(0,0,0,.3)) !important;
}
#tab-bar-container .tab:not(:first-child) .tab-close {
filter: invert(0.7);
}
#zotero-toolbar {
background: inherit !important;
border-bottom: inherit !important;
}