I think, you are talking about Project Explorer in Mendix Studio Pro
You can get it by following this steps.
First Click view button in the top left corner of the Mendix Studio Pro.
Then click Project Explorer menu to open it.
Do you mean an overview of all your projects? Like in sprintr: https://sprintr.home.mendix.com/link/myapps
When you open up the modeler and you have signed in you also get a view off all your recent open apps.
Or am I missing what you are looking for?