Comparing Spectacle with other screenshot tools, we can notice that we lack the function of tasks that are done after a screenshot has been made.
Other tools have, for example, the ability to automatically upload it to an imagehost, ftp server, etc.

I've made this small draft, with the intention to add much more tasks the user could do.
This one, in the screenshot below, allows the user to call any program/bash/python script after the image has been saved.
With this simple addition, an advanced user can easily make an own script/program that, for example, uploads the picture somewhere. The default argument would be the location of the image. So an user can easily grab it in a *.sh via $1.
Adding more built-in tasks should be appreciated more by users who are not familiar with making scripts.

Currently we have the Export function that enables us to either send the screenshot via mail or upload to online services. But this has to be called manually.
Tasks would enable to automatically upload a screenshot to a desired host, or send it via mail, etc.

Currently WiP:
https://phabricator.kde.org/D23366