You can organise the list into the order you want. Perhaps the issue is that you are sorting the playlist by a specific criteria, other than manual.
Open the playlist and make sure that there is an arrow in the left column, which is the manual sort order column. If it's not there, it means that the playlist is being sorted by a different column, which will mean you cannot sort it yourself. You can click on the left column header to get the arrow there and then you will be able to sort it yourself. If the arrow points up, the sort order would have been first added to list through to last added to the list, until such time as you changed the order. If the arrow is down, the sort order is reversed. Click on the header again to reverse the arrow.
Here is the same playlist, but notice the difference:
In the above screenshot, I cannot manually sort that playlist. But when I click on the header above the numbering:
Now I can manually sort the playlist.
By the way, if you want the playlist in alphabetical order, simply click on the Name column header: