Several Slack apps (e.g. Twitter, Google Calendar) provide a configuration page after installation into Slack. However this feature seams to be available only to commercial partners of Slack, but not as a standard feature for every app developers.
Developers need to implement it by themselves with an external app / script that is linked the Slack app and store the configurations in their own database.
See also this answer for a full explanation on how this works.
You can now use Dialogs to create something similar to configuration pages. It allows you to open a custom modal window with up to 5 inputs (text or drop-downs). Its still not the same as having a full configuration page like the internal Slack apps have, but its a huge step forward and might be sufficient for many cases.
Several Slack apps (e.g. Twitter, Google Calendar) provide a configuration page after installation into Slack. However this feature seams to be available only to commercial partners of Slack, but not as a standard feature for every app developers.
Developers need to implement it by themselves with an external app / script that is linked the Slack app and store the configurations in their own database.
See also this answer for a full explanation on how this works.
Looking on the official Slack Plattform Roadmap for Developers this feature might be implemented in the future under "Install apps from within Slack".
Update:
You can now use Dialogs to create something similar to configuration pages. It allows you to open a custom modal window with up to 5 inputs (text or drop-downs). Its still not the same as having a full configuration page like the internal Slack apps have, but its a huge step forward and might be sufficient for many cases.