I Know that it is possible to re-arrange by cutting and pasting but that can be laborious in lasrge trees.
No matter which order you select them, as long as you enter the DATE especially YEAR they will appear in Datal order .
If you start to enter in the wrong order such as Death then Marriage then Birth. As long as you put the correct Dates it then sorts out the Correct order of Birth Marriagr and Death. If you return at a later Date and you add a different Source you will find that as long as you have put a Date, it will be entered somewhere in the List in Datal order
Try playing around with a NAME as you can always DELETE the SOURCES entered..
All the best
Les