Example
You are in fort game mode (0 game mode), managing your fortress (0 control mode) and go into the Esc menu(in Dwarf fortress it's the place where you save the game), You switch to the Adventure game mode (1 game mode in DFmode) and switch to the managing(which is 0), then save the game. You just left a fortress to play as an adventurer. Leaving the site will count the site as abandon and kill off all pets and tamed. If you want to choose who you want to play as then pick up Dfusion and use either the Adv_tools Adventurer changer or the Tools version. Tools version saves you the hassle of stacked creatures which the pointer won't work on very well. While adventurer tools ?Change? save you hassle for searching for a certain creature that you can plainly see.
Oh you can also return to the fort(the imput to do this is 0,0 or 0,1) if:
Your adventurer is on the site,
The adventurer/fort members has the is resident flag off.
the adventurer could have the same civ, though this is only vital for making adventurers work at the fort.
The adventurer on a previously active fort, other forts will work for a few in game days then DF boots you out of fort mode with a the force abandon.
I take no responsibility of anything that happens as a result of using this tool :P
here my take on the DFmode example, langdon's retire fort trick would be a nice add on to the readme as well.