Can i add more custom Hit Effect Option in GLOBAL EDITOR ?

If you have moves that require custom hit effects, you can override the move's hit effect in Active Frames.  I would suggest this way first, especially if said effect is only used by few moves.

If you absolutely require more regular hit effects than the 9 currently available (as of 1.6), then it should be possible to mod that in.   Look in GlobalInfo.cs for:

public class HitOptions {

Then go into ControlScript.cs and look for any instances of UFE.config.hitOptions and add your new customs anywhere it looks for the regular effects.

For the extra custom body parts - are the 9 extra customs not enough?  If not, just add more.  GlobalInfo.cs:

public enum BodyPart {

Similar deal as above with the hit effects; look for anywhere that it looks for specific bodyparts and ensure yours is included.

Only issue I can see with the extra body parts is the mirroring.

Have you gone through the Throw Tutorial?  It deals with Opponent Override, and might be easier to understand.

Here's how you can set up your example though:
- Create 3 moves for your sHP: Attempt/Confirm/Reaction.  Attempt is the sHP as if it misses (but include the active frames here, also the only one with an input); the Confirm is what it cancels into when hit, and it's this Move that will have the Opponent Override in it; and the Reaction is the Opponent's reaction you'll be overriding with.
- In sHP_Attempt, create a Chain Link during the active frames, the Move Link is the Confirm, and set Auto Execute on.
- In sHP_Confirm, in Chain Link put sHP_Attempt as required move.  Don't forget to add sHP_Reaction to the Opponent Override.

That should get it working.

It can be a little tricky to grasp, so just keep trying at it.  The Throw Tutorial goes through a very similar process, but it uses Throw Hit Type specifically, so not exactly the same.