Making an agenda that includes scheduled-for-later tasks?

[Leo Gaspard <orgmode@leo.gaspard.io>]

Hello all!

I am trying to make an agenda view of all tasks that don't have the
:Effort: property set, including tasks that are scheduled for later.

My init.el files includes the following lines (of interest is the "E"
agenda):
```
(setq org-agenda-custom-commands
      '(("U" "Unscheduled tasks"
	 todo '("TODO" "WAITING")
	 ((org-agenda-overriding-header "Unscheduled tasks")
	  (org-agenda-skip-function '(org-agenda-skip-entry-if 'scheduled))))
	("E" "Effortless tasks"
	 todo '("TODO" "WAITING")
	 ((org-agenda-overriding-header "Effortless tasks")
	  (org-agenda-skip-function '(org-agenda-skip-entry-if 'regexp ":Effort:" 'todo '("APPT")))))))
```

However, for some reason only tasks that are either not scheduled or
scheduled for some time in the past show up in this agenda. This makes
it useless, as the point is to remember to put in efforts for every
task *before* they are scheduled (and thus started)

Do you have an idea what I could have missed?

Thanking you in advance,
  Leo

PS: Also, I've noticed setting =todo '("TODO" "WAITING")= is apparently
not enough to get it to ignore the APPT-tagged items, so I've added the
filter to =org-agenda-skip-entry-if=. If you have an idea what I'm doing
wrong…