Giving step-by-step instructions for all possible scenarios is just too much (seriously, maybe you should download YEM manual).
Here I will try to give you only some general info's -so you know the general approach..
If you have unprotected PackA & PackB packs (*.ppf file extension), then you can create new pack in YEM and put (import) whatever you wish (from pack A & B) into it your pack. Additionally you can add styles, registrations, voice settings, etc into your newly created pack. The only thing you need to care of, is it's size. When you're finished with creating your pack, you can export it as "MyHitsNr1.ppf" (for archiving purpose), or you can save it as Pack install file (MyHitsNr1.ppi -for example).
That is, your created pack will be shown as "MyHitsNr1" (with all content in it) when you install it in keyboard.
In case your PackA & PackB packs are protected (have *.cpf extension), then you can still select what you wish in your pack, but you can't move that selection into your pack. That is, even you name your pack "MyPackNr1" (at creating install file) and install it on keyboard, the content will be separately shown as PackA and PackB. I know it sounds complicated, so let me explain:
Say you have two cpf packs: Salsa and Brasil. Let's say you wish to combine content of these two packs, so that you would end up with only one "Latin" pack -you can't do that with cpf packs. Of course you will save something from both packs as a single installation file (Latin.cpf), but after you install it, you will see two packs listed: Salsa and Brasil.
There are other things you can't do with cpf packs, but it depends on your usage how big limitations that are for you. With unprotected packs (ppf), you can combine things as you wish.
Ah yes.. in case of unprotected packs, you can use them also if they're not made especially for SX700 (once you know where you need to pay attention). However, if pack is protected, it must be made for SX700 (otherwise you can't create install file for SX700).
This are some general hints, so you don't wonder "why I can't do that?". The rest is up to practicing with YEM.
Bogdan
