Anywhere adds the load_level command, which allows you to access any level at any time, including many dev levels that currently aren't accessible with vanilla Gungeon. As an added bonus, you can also reskin some of those levels, allowing you to play in a futuristic complex or the guts of some titanic beast.
A couple things to try:
load_level resourcefulratlair_flow, then, if you can't make it through the maze (quite likely there is no path) tp 350 25
load_level demo_stage_flow future

Warning: the load_level command CAN and WILL crash your game if you try to go to a REALLY unfinished level or try to load any of the main dungeons with an alternate skin. Don't use it in the middle of your best run ever unless you already have a feel for what will and will not crash the game!