You can certainly put it anywhere in the chain that you like. You’re not going to break anything. After all a Leslie simulator is just a very fancy combination of

Tube amp emulation to emulate the power amp of the Leslie.
Synchronzied flanging and tremolo to emulate the spinning rotor.
Filters to emulate the combination of woofer and horn.

But, think about the sonic image you’re attempting to project and what the pedal is supposed to do. Imagine that you were using a real Leslie speaker/amp. Would that go at the beginning of your effects chain or at the end? At the end of course because everything would have to plug into it.

What if you want to use the stereo output to actually make the sound physically swirl around the room. You can’t do that by putting it at the front of your effects chain unless every single effect after it is also stereo. If you want to do real stereo, you’re pretty much going to have to put it at the end of your effects chain, right before the board or your two amps.

Speaking of going into a board, either a live mixer or a recording system, the Lester is an amp & cabinet simulator in the very best sense of the word. It’s a cabinet sim on steroids. Normally cabinet sims are the last thing in the chain right before the DI box, the DAW, whatever. They are intended to make the signal sound like you’re micing an amp and/or cabinet, rather than going directly into the mixer which sounds terrible. In general any amp/cabinet simulators would go at the end of a chain. Obviously things like Radial and “Two Notes” active DIs with amp/cab simulation HAVE to go at the end. Tech 21 and other SansAmp like DIs also have to go at the end of the chain. The EHX Battalion and Bass Metaphors are designed to go at the end of the signal chain. The EHX Tortion is designed to go at the end of the chain if you use it as a DI. All of these are amp/cab simulators. The Lester G is the most complex amp/cab simulator of them all.

As far as the issue with having a compressor, there are some options. You could just not use it. In fact, lots of guitar players get the Lester K because they already have a compressor and they don’t need the one in the G. Or, you can play with it to get the compression level correct. A compressor, in contrast to a limiter, does TWO things. It both LIMITS the signal and BOOSTS the signal. It squashes sounds that are too loud and boosts sounds that are too soft. If you are producing much more volume than the amount of noise in the signal, then when you squash it down it will squash the noise even lower. A compressor used in the right way can actually reduce the noise in your signal. By using the right amount of sustain, attack, and “squish” setting, you should be able to dial in a reasonably quiet signal, certainly while you’re playing. The key is to avoid the temptation of using too much sustain.

Of course, your mileage may vary. The only way to really figure out what works for you is to try it. Again, you won’t break anything.

You are the music-maker,
And you are the dreamer of dreams,
Wandering by lone sea-breakers,
And sitting by desolate streams…

Wow. That’s good to know. The Platform is a great compressor.