In order to keep the pages in the system administration guide in sync with the OpenProject application, the order of the pages should be the same as in the application Administration. 

Page Hierarchy of the System Administration Guide

999 Initial Setup
990 Users and permissions 
980 Work packages
970 Custom fields 
960 attribute help texts
950 enumerations
940 working days 
930 system settings 
920 emails and notifications
910 api and webhooks - add a system guide page for API and Webhooks, move the API page from System settings ( #44906 )

900 authentication
        IS ALL AUTHENTICATION INFO STILL VALID? 
890 GDPR - add a system guide page for GDPR settings (#35680 )
880 announcement
870 design
860 colors
850 time and costs
840 backlogs
830 file storages - add a system guide page for file storages and link to the Nextcloud Integrations subpage. 
        currently there is a link to the respective page in the app doing just that - not critical
820 billing - needs ot be added (#45602 )
810 slack integration - needs to be added (#45601) 
800 plugins
790 backup
300 information
200 integrations
100 System Admin FAQ