Hi Martin,
Unfortunately, this is a windows issue that I have had with other apps as well e.g. GitHub.
What has worked for me is:
- change scaling. If it is set to 125 or 150 for your laptop screen you can scale it down to 100% and then hopefully you can see the modeler
- change the default monitor to the second screen.
- Shift+Right click the modeler window in the screenshot to get the context menu and then try to either 1) move or 2) maximize / restore
- right click on the taskbar and cascade all windows
Hope one of these works for you
-Andrej
== EDIT 24 Apr 2019 ==
See below comment for solution.