Make `org-agenda-view-columns-initially' a defcustom

* lisp/org-agenda.el (org-agenda-view-columns-initially): New variable,

etc/ORG-NEWS

@@ -208,6 +208,8 @@ When defining a "columnview" dynamic block, it is now possible to add
 an :indent parameter, much like the one in the clock table.
 
 On the other hand, stars no longer appear in an ITEM field.
+*** New variable : ~org-agenda-view-columns-initially~
+The variable used to be a ~defvar~, it is now a ~defcustom~.
 *** Preview LaTeX snippets in buffers not visiting files
 *** New option ~org-attach-commit~
 When non-nil, commit attachments with git, assuming the document is in

lisp/org-agenda.el

@@ -1950,6 +1950,14 @@ category, you can use:
   :tag "Org Agenda Column View"
   :group 'org-agenda)
 
+(defcustom org-agenda-view-columns-initially nil
+  "When non-nil, switch to columns view right after creating the agenda."
+  :group 'org-agenda-column-view
+  :type 'boolean
+  :version "25.1"
+  :package-version '(Org . "9.0")
+  :safe #'booleanp)
+
 (defcustom org-agenda-columns-show-summaries t
   "Non-nil means show summaries for columns displayed in the agenda view."
   :group 'org-agenda-column-view

lisp/org-colview.el

@@ -1387,9 +1387,7 @@ and tailing newline characters."
 
 ;;; Column view in the agenda
 
-(defvar org-agenda-view-columns-initially nil
+(defvar org-agenda-view-columns-initially)
-  "When set, switch to columns view immediately after creating the agenda.")
-
 (defvar org-agenda-columns-show-summaries) ; defined in org-agenda.el
 (defvar org-agenda-columns-compute-summary-properties); defined in org-agenda.el
 (defvar org-agenda-columns-add-appointments-to-effort-sum); as well