Editing data in PkHeX; checksum doesn't change

[Misdreavus]

Awhile back, I edited my game's playtime in PkHeX to force the checksum to be a value that yields a shiny Jirachi from the Colosseum Bonus Disc.  I'm trying to do that again; however, I'm not sure what exactly I did the first time, and I'm having a bit of difficulty.  Here's what I'm doing:

1. I open the .sav in HxD Hex Editor and locate the checksum.

2. I open the .sav in PkHeX and edit the playtime.

3. I go to File -> Export SAV -> Main and save my file.

4. I locate the file and manually add .sav to the file name.

5. I open the new file in HxD, browse to the same location I found the checksum at in step 1, and view it.

The checksum doesn't change though.  Why would this be?  Am I doing something wrong?  I know if I do it properly it should change since I've done this before (with an earlier version of PkHeX).

[Kaphotics]

you likely edited the backup save file, not the active one

(the sav stores two files in the event one is corrupt).

[Misdreavus]

2 hours ago, Kaphotics said:

you likely edited the backup save file, not the active one

(the sav stores two files in the event one is corrupt).

I'm familiar with the two save banks; however, I wasn't aware that I had a choice in which one I edited.  How do I change between them in PkHeX?

[Kaphotics]

You'd need to edit the active save file instead of a fixed offset.

PKHeX detects the active save file by looking at block0's update counter; the higher of the two is the most recently updated save (ie active). The active save is what is edited by PKHeX, and is the save that is loaded when the game boots.