AT:
- In the variable filter, if there is a list of variable values, I can check multiple of them
- Selecting multiple variable values is only possible for the operators Is and Is Not
- If the operator is Is Not, multiple values are combined with an AND operator (this will be done by the backend)
- If the operator is Is, multiple values are combined with an OR operator
There are some minor issues with code style and I don't like user experience. See comments to commit for details.