Give that a go. You should have 9,999,999 rupees assuming the game didn't add a checksum in an update or something weird like that. I also might have messed up, it's been a while lol. I can redo it if it isn't right either way.
If the current save editor doesn't work, I might pick up the game again and just throw together something basic if I have the time in the next few weeks.
Edit:
Yeah I think I did it wrong the first time, try this one instead...
Edit 2:
After manually doing the edits, I did notice that the save appears to open fine in the current save editor, so I imagine that would work going forwards if you do want to do it yourself: