org-agenda-sorting-strategy

org-agenda-sorting-strategy is a variable defined in `org-agenda.el'.
Its value is

((agenda habit-down time-up priority-down category-keep)
 (todo priority-down category-keep)
 (tags priority-down category-keep)
 (search category-keep))

Documentation:
Sorting structure for the agenda items of a single day.
This is a list of symbols which will be used in sequence to determine
if an entry should be listed before another entry. The following
symbols are recognized:

time-up Put entries with time-of-day indications first, early first
time-down Put entries with time-of-day indications first, late first
timestamp-up Sort by any timestamp, early first
timestamp-down Sort by any timestamp, late first
scheduled-up Sort by scheduled timestamp, early first
scheduled-down Sort by scheduled timestamp, late first
deadline-up Sort by deadline timestamp, early first
deadline-down Sort by deadline timestamp, late first
ts-up Sort by active timestamp, early first
ts-down Sort by active timestamp, late first
tsia-up Sort by inactive timestamp, early first
tsia-down Sort by inactive timestamp, late first
category-keep Keep the default order of categories, corresponding to the
sequence in `org-agenda-files'.
category-up Sort alphabetically by category, A-Z.
category-down Sort alphabetically by category, Z-A.
tag-up Sort alphabetically by last tag, A-Z.
tag-down Sort alphabetically by last tag, Z-A.
priority-up Sort numerically by priority, high priority last.
priority-down Sort numerically by priority, high priority first.
todo-state-up Sort by todo state, tasks that are done last.
todo-state-down Sort by todo state, tasks that are done first.
effort-up Sort numerically by estimated effort, high effort last.
effort-down Sort numerically by estimated effort, high effort first.
user-defined-up Sort according to `org-agenda-cmp-user-defined', high last.
user-defined-down Sort according to `org-agenda-cmp-user-defined', high first.
habit-up Put entries that are habits first
habit-down Put entries that are habits last
alpha-up Sort headlines alphabetically
alpha-down Sort headlines alphabetically, reversed

The different possibilities will be tried in sequence, and testing stops
if one comparison returns a "not-equal". For example, the default
'(time-up category-keep priority-down)
means: Pull out all entries having a specified time of day and sort them,
in order to make a time schedule for the current day the first thing in the
agenda listing for the day. Of the entries without a time indication, keep
the grouped in categories, don't sort the categories, but keep them in
the sequence given in `org-agenda-files'. Within each category sort by
priority.

Leaving out `category-keep' would mean that items will be sorted across
categories by priority.

Instead of a single list, this can also be a set of list for specific
contents, with a context symbol in the car of the list, any of
`agenda', `todo', `tags', `search' for the corresponding agenda views.

Custom commands can bind this variable in the options section.

You can customize this variable.