chas is right...  the signal flow is pretty much pre-determined...  most of the time the way it's set up is the way that you would set it up anyway, although, i would agree with anyone that supports "anything-to-anything" routing...

the way i think about it is like this:

you have your GATE, WAH, STOMP, AMP+CAB, COMP and EQ blocks...  these are the blocks that don't have a PRE/POST option, and as long as the blocks that do have a PRE/POST option are set to POST, these 6 blocks will always be in the same order...

then you have your VOL, LOOP, MOD, DLY, VERB blocks...  these blocks all have PRE/POST options...  when one of these blocks is in PRE mode, it will be before the AMP+CAB block (and after the STOMP block)...  when one of these blocks is in the POST mode, it will be after the EQ block...

whether or not these blocks are in PRE or POST mode, they will always be in the same order with respect to eachother...  for example, if all of these blocks are in PRE mode, the block order for the whole chain will be:

GATE > WAH > STOMP > VOL > LOOP > MOD > DLY > VERB > AMP + CAB > COMP > EQ

if all these blocks are in POST mode, the block order would be:

GATE > WAH > STOMP > AMP + CAB > COMP > EQ > VOL > LOOP > MOD > DLY > VERB

however, let's say you want to put the VOL and VERB blocks in the PRE position, but the rest in POST position, the block order would be:

GATE > WAH > STOMP > VOL > VERB > AMP + CAB > COMP > EQ > LOOP > MOD > DLY

as you can see, the PRE blocks maintain thier order and the POST blocks maintain thier order...  yes, the VERB block is before the LOOP, MOD, and DLY blocks in the entire chain, but only because the VERB block is set to PRE and the LOOP, MOD, and DLY blocks are set to POST...  there is no way to have, say, the VERB block be before, say, the VOL block without putting the AMP + CAB, COMP, and EQ blocks in between them...

so, you can see that this is certainly not "anything-to-anything" routing, which would be preferable and more condusive to experimentation, but like i said, in most cases, the way it is set up should be able to accomplish what you're looking for...