https://github.com/Healix/Gw2Launcher/blob/master/README.md


-Gw2Launcher-

GW2 uses a mutex to prevent multiple instances from being opened at the same time.
In addition, GW2 also locks access to GW2.dat, which prevents other processes from
reading it. By killing the mutex and enabling -sharedArchive, multiple clients can
be launched simultaneously.


-Local.dat-

Local.dat is the file used by GW2 to store settings related to your computer, such
as your login information and video options. Only 1 Local.dat file can be active on
a single Windows user account at a time. In order to run multiple clients with
different settings, each client will need to use a different user's account. This
program will assist in the creation and management of additional users if needed.

When -sharedArchive is enabled, GW2 will not be able to modify any files. In order
to update the game or modify your settings, the game must be launched normally.

Gw2Launcher will manage your Local.dat file and allow for multiple GW2 clients to be launched simultaneously.


-Installation-

Simply download the 64-bit or 32-bit version and place the executable wherever you'd like. This program does not need to be installed. Note that the 64-bit executable is required if running GW2 in 64-bit.


-Settings / General-

-Windows user account-

For your first account, you can leave this blank to use the account you're currently logged in to. For future accounts however, you'll need to use a unique user account if you want GW2 to use different settings (including the remembered login). If you need to create a user account, simply type in a new name. You'll be asked if you want to create the user now, or you can choose to do so manually through Windows later. Note that user account management functions will require administrative access to execute.
Settings / Local.dat

Select the Local.dat file you want to use with this account. If you already have one, choose to move it.


-Launching-

Click the account's button to launch the account. If you have not yet set the path to GW2, you will be prompted to do so now. To change the settings, right click an account button or the tray icon to bring up the menu.

On your first launch of each unique Local.dat file, you will be asked if you want to launch the game normally to modify your settings. When GW2 is sharing access, your settings will not be saved and GW2 will fail to update.


-Cache folders-

CoherentUI, the in-game web browser used for the trading post, may create temporary cache folders every time GW2 is launched. This can quickly lead to a hundreds of megabytes of wasted space.

Select the option to delete cache folders under tools to manually delete these folders, or to setup automatic deletion. Note that these files are temporary and can safely be deleted.


-Hidden users

Additional user accounts are required to use individual settings on multiple simultaneously active accounts. If you've setup users for just this purpose, you may want to hide them from the system, as they will be displayed on any login screens.

Select the option to hide user accounts under tools to choose the users that you want to hide. These accounts will be disabled when the program is exited and enabled when the program starts. Disabled users will not be able to be logged in to. Note that administrator access is required to setup this option.