I have a huge custom list with several columns. They are grouped by e.g. Status, but the order of the groups cannot be influenced as it is strictly alphabetical. Is there a (nice) way how to customize the order of the groups within the list without using prefixes for the Status, e.g. 1_Initiated, 2_Started, 3_Completed?
You could create a hidden column where you have a calculated column with an IF statement giving each value e.g.
IF([Status]="Initiated",1,(IF([Status]="Started",2,IF([Status]="Completed",3))) and so on. Use this then to order the group.
Look at how quick launch links are ordered in SharePoint or how columns are ordered in a view. This is the closest SharePoint comes to having a user customizable order. And STILL this functionality is not available as a column type for a list or library.
So, sorry, NO this is not possible with OOTB SharePoint.
But, in a post by Stump the Panel from 2009 they prove you CAN do this if you start with a link list!