前提
Firefox 设置
访问 about:config，开启 toolkit.legacyUserProfileCustomizations.stylesheets
Sidebery 设置
Sidebery settings > Help > Preface value: [Sidebery]
在 Firefox 配置文件夹中新建 chrome 文件夹，并在文件夹中新建并修改 userchrome.css
/* Hide the tabs when Sidebery visible */
#main-window[titlepreface*="Sidebery"] #TabsToolbar-customization-target {
height: 0 !important;
overflow: hidden;
}
/* Make the application min-maximize-close buttons height match the address bar */
#main-window[titlepreface*="Sidebery"] #TabsToolbar .titlebar-buttonbox-container {
height: 40px;
}
/* Push up the address bar */
#main-window[titlepreface*="Sidebery"] #nav-bar {
margin-top: -41px;
}
/* Reduce width of address bar so app buttons have enought room to appear */
#main-window[titlepreface*="Sidebery"] #nav-bar-customization-target {
max-width: calc(100vw - 230px);
}