How can I store variables in all levels?

You could try way mentationed in What is the best way to keep data between levels? - World Creation - Epic Developer Community Forums i.e.

"Config Files
For very small amount of data you can simply save it out to config file and then load it back

Binary Save and Load
I have tutorial on how to save any data you want to compressed binary file and then load it back into game!



I found that in UE 4.4 is UGameInstance class that is persistent between levels. You can try using it.