The similar question was asked earlier https://forum.mendixcloud.com/link/questions/109984
The solution proposed by Tim there would work for you:
in StudioPro in your project explorer go to Navigation Select a microflow instead of a page, as Home page. In the microflow, you can access the session id and also after this show whatever page you would like to show.
After-Startup microflows are run as part of the loading process for a Mendix application. This occurs before there are any users using the application, hence the current user and session not being available.
Hope this helps.
you can create a custom rolebased homepage in the navigation, set it to microflow, in which the session id is available and you check if the object is associated and if not create it.
If you don't like this, you can create a custom login handler in which you create this object after successfully logging in to the application.