tested under:

Linux laptop 3.16.0-4-686-pae #1 SMP Debian 3.16.7-ckt20-1+deb8u3 (2016-01-17) i686 GNU/Linux

in terminal you will find that

gnome-session-properties

was removed gnome startup-applications-preferences was removed

but you can use

gnome-tweak-tool

which should be pre-installed.

tweak tool gnome3

which lets you easily manage the upstart / autostart.

gnome-tweak-tool screenshot - autostart

and many other things:

tweak tool gnome3_10

tweak tool gnome3_9

tweak tool gnome3_8

tweak tool gnome3_7

tweak tool gnome3_6

tweak tool gnome3_5

tweak tool gnome3_4

tweak tool gnome3_3

tweak tool gnome3_2

tweak tool gnome3_1

Creditz:

http://www.stylesen.org/gnome_3x_startup_applications_debian_jessie

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