select-tab-macro.el

(defmacro ct/tab-bar-select-action-define (num)
  `(defun ,(intern (format "ct/tab-bar-select-%i" num)) ()
     ,(format "Select tab %i by its absolute number." num)
     (interactive)
     (tab-bar-select-tab ,num)))

;; Manual calls work
(progn
  (ct/tab-bar-select-action-define 1)
  (ct/tab-bar-select-action-define 2)
  (ct/tab-bar-select-action-define 3)
  (ct/tab-bar-select-action-define 4)
  (ct/tab-bar-select-action-define 5)
  (ct/tab-bar-select-action-define 6)
  (ct/tab-bar-select-action-define 7)
  (ct/tab-bar-select-action-define 8)
  (ct/tab-bar-select-action-define 9))

;; Helper to undefine the functions again 
(progn
  (fmakunbound 'ct/tab-bar-select-1)
  (fmakunbound 'ct/tab-bar-select-2)
  (fmakunbound 'ct/tab-bar-select-3)
  (fmakunbound 'ct/tab-bar-select-4)
  (fmakunbound 'ct/tab-bar-select-5)
  (fmakunbound 'ct/tab-bar-select-6)
  (fmakunbound 'ct/tab-bar-select-7)
  (fmakunbound 'ct/tab-bar-select-8)
  (fmakunbound 'ct/tab-bar-select-9))

(ct/tab-bar-select-action-define 1)
(let (tab-number)
  (dotimes (i 9)
    (setq tab-number (+ 1 i))
    (message (format ">%i" tab-number))
    (ct/tab-bar-select-action-define tab-number)))

;; Compiler-macro error for cl--block-wrapper: (error "Format specifier doesn’t match argument type")
;; intern: Format specifier doesn’t match argument type

Thanks to @daviwil's feedback and documented fixed in https://gist.github.com/daviwil/3215f99db0ac0cb122a9a1850f400594 I realize that passing arguments to macros isn't worth the trouble when you have to inline the loop anyway -- so might as well do it directly:

  ;; Bind 1-9 in the tab prefix map to switch to that tab.
  (mapcar (lambda (tab-number)
            (let ((funname (intern (format "ct/tab-bar-select-%d" tab-number)))
                  (docstring (format "Select tab %d by its absolute number." tab-number))
                  (key (kbd (format "%d" tab-number))))
              (eval-expression `(defun ,funname ()
                                  ,docstring
                                  (interactive)
                                  (tab-bar-select-tab ,tab-number)))
              (eval-expression `(define-key tab-prefix-map key ',funname))))
          (number-sequence 1 9))

This enabled SPC t 1--SPC t 9 to switch to the tab by number directly.