You have to change each track individually by editing 1 line of the tracks .GDB file found in Gamedata/Locations/*Track Name* folder
The line you want is 'Category' and for most add-on tracks this is below the track name and track info lines. Usually for add-ons this is "Category=Add-On"
Changing the word 'add-on' to whatever category you want the circuit to be sorted as will change the tracks sorting, e.g. BTCC or whatever.
I hope this helps!
Edit: having read your post again if you mean changing the order of the add-ons you have to add in a line 'EventDate' to the .GDB file.
Some tracks might have them already but otherwise just add in this line with the date you want, for example:
EventDate = 7-8 July, United Kingdom
The track will now move to the top of the add-ons list with all other tracks with an EventDate sorted in date order.
I think this is what you meant now!