A more modern visual representation for tab-bar-mode tabs. Note that this does not affect tab-line-mode tabs.

(modern-tab-bar-mode 1)

Ensure that modern-tab-bar-mode is enabled after your primary theme.

You will need to remove or revisit any customizations you have for the variables that modern-tab-bar sets via a custom theme. Note that your customizations may take precedence over modern-tab-bar, depending on how they are set.

tab-bar-format

Set modern-tab-bar-format instead

tab-bar-separator

Set modern-tab-bar-separator instead

tab-bar-tab-name-format-function

Set modern-tab-bar-tab-name-format-function instead

tab-bar-auto-width

This must be nil or it can cause Emacs to hang

This package is not on MELPA, so you must install it manually or use something like elpaca.

(use-package modern-tab-bar
  :ensure (modern-tab-bar :host github :repo "aaronjensen/emacs-modern-tab-bar" :protocol ssh)
  :init
  (setq tab-bar-show t
        tab-bar-new-button nil
        tab-bar-close-button-show nil)

  (modern-tab-bar-mode))

M-x customize-group modern-tab-bar

The faces in the modern-tab-bar-faces group can be adjusted or themed as well.