I can show you how to make a playlist on the phone and manage it with a PC. If you want to do this read on. If you don't want to use a PC stop here.
Make a playlist on your phone. This just gives you a starting point, doesn't make any difference if it is one song or an album. Start an album or song playing, below the album art tap the song name. Another page pops up, tap the save icon on bottom, now you give your playlist a name. You have made a playlist on the phone. Pause the player
Manage the playlist in Win7. Do this with playlist created with the phone. Not with playlists you have created in some other way.
Connect the phone via USB to the PC.
With windows explorer find your playlist. It is in the playlist folder in music. On the SD card if you have one, if not it is on the phone.
Double click the playlist file you just created or right click it, properties, reference tab. This will open the reference tab window.
You can now
add to the playlist from songs on your phone using drag and drop into the refercnce tab window.
From the resources tab window you can also delete songs from the playlist and set the play order.
In Win8.1 the playlist folder is hidden and the window is called recources instead of refercnce. You will have to figure out for yourself how to view hidden files and folders.
Again, just with music on your phone, not in the cloud. This will fail.