They should be on the mod launcher in the [Settings] tab

If you want to have all unlocks, you can use the cheats in the mod launcher.
On the settings tab, you'll see some settings. Enable the following:

Unlock All Rewards
Unlock All Missions
Starting Coins

I have the cheat keys mod. Is this the one ? Because I don't see the settings you're talking about in my game.

Thank you

Thank you. The Invisible bart mod isn't worth starting over, I'll keep the game this way.

Since BKP is a main mod, I doubt. Also, the two mods aren't compatible with each other because they modify the same file I assume

Ok, so I just tried launching the game without any mods on and the third save worked. But neither of the 2 others were there.

Tried again with only the Borb's BKP Pack on and my two saves are there. It seems it worked. But I'm now in level 2 with Bart, so I want to use the Inivisble Bart mod. I can't have both these packs on at the same time. Can I play with my saves without the BKP mod ?

Some mods have a Main=1 flag which makes them create their own save game files.
You can find these in Documents/My Games/Lucas' Simpsons Hit & Run Mod Launcher/Saved Games.
I'm not sure why your game would not load the saves even after playing without mods, could you list every mod and setting that you have ticked on the launcher?

Sure. I use the Borb's BKP Pack, ther Minor Fixes pack, the 3D phone booth previews and the cheat keys. The location you just told me is exactly where my saves are, but not the third one (weird). It also seems like the mod launcher created a sub-folder called BorbsBKPPack in the Saved Games folder. I tried putting the saves out of the folder and directly in the saved games one but the game still doesn't recognize the saved files.