That's basically what I mean. It would be great to dial up a SRV Tubescreamer sound, or a delay that sounds like The Edge and save those parameters in a Favorites list, then while you're in a different preset you can just pull that SRV sound back up. It could work like this: Press the joystick button to assign a new block, in the scrolling list below NONE and DISTORTION have a FAVORITES list that you build by assigning your most used blocks. This would save me a ton of time.
And then to answer your "I would rather have fewer overall available slots for presets if I can save as many of the same effect as I want within those available slots." issue, take a deeper look at snapshots. First access your global settings menu, select footswitches and on the second dial, scroll to Snap\Stomp; now in a preset when you hit the mode button, instead of having all eight footswitches used as stomp switches, only the bottom four buttons will be your stomp switches, and the top four buttons are snapshot buttons. With snapshots, you are able to change any of the parameters of all of your blocks for instant toggling. You can change gain on your amp, change the microphone placement, turn on an overdrive, turn off a phaser, and crank up the repeats on your delay all with one button. It's kind of like using a bypass looper that does multiple functions while only pressing one thing. That said, you can accomplish your ten different Tubescreamer sounds fairly easily. It's definitely worth looking at. You can also rename your snapshots.