I will second Keith's statement of using a dummy account. While rejoining as a player works great for certain spot checks, dummy accounts are extremely useful when setting up Dynamic Lighting barriers as well as other things. * You can spot check your work to make sure Roll20 is seeing it. People have lost hours of work because there was a desynchronisation between what they were doing and what Roll20 saw. Logging in with a dummy account lets you spot check your work while you are setting it up. * You can have two tabs open on the same account, one in player mode and one in GM mode, but that can lead to some unexpected side-effects and issues. Using a dummy account on a separate browser resolves that and prevents you from having to switch to player mode, test something, switch back, etc.