There are many ways, how user specific settings can be used and stored in ECTR.
Here's an overview:
There are settings, which are stored as parameters in the ABAP backend user profile
You can use parameters in the transaction SU3 to define default values, e.g. /DSCSAG/PLM_LABOR
Those parameters are also available in ECTR. You can see them in Preferences Browser:
You can move those parameters als into the local user preferences, see How to move SAP user parameter into ECTR preferences.
There are settings, which are stored in the user.txt and gui.txt
A lot of settings of the current session are stored in %AppData%\Roaming\SAP\ECTR\data\<ECTR installation ID>\<SAP ID>_<client>_<User ID>\preferences. These settings are written when ending the session and read again when starting the next session. This is stored locally in the user's AppData directory and might be only available on a specific frontend.
The settings in preferences folder can be up-/downloaded from backend
The settings from %AppData%\Roaming\SAP\ECTR\data\<ECTR installation ID>\<SAP ID>_<client>_<User ID>\preferences can also be uploaded into the SAP backend into a Document Info Record with DocType=AUX, DocNumber=<user ID>_LU (LU = last used) DocVersion=00 DocPart=000.
The user can trigger this via the menu:
A restart after loading the configuration is strongly recommended.