I have a list of filenames in sharepoint. I was asked to put them in a certain order, not sorted by any particular field, just an order I was given. How do I do this?
You can create one column with name "OrderID" with Number or Single line text column type with set YES for Enforce unique values. Now set the order of the file name by assigning the number in "OrderID" column. Edit the view and sort the view using "OrderID" column.
This would be the easiest way to do custom ordering. Even if you want to change the order of the file names just open the view in quick edit mode and re-assign the numbers in "OrderID" column. It will work like a charm for you.
SharePoint List itself has ID (item id no), Modified/Created (Date Time) column which will sort the items, also on custom Single line text column you can do sorting. You can also make the combination of two columns for sorting.
If this is not sorting as per you required, then you can try the solution explained by Dikesh.