While testing, I've noticed a couple of things that could be improved in the variable filter modal. These are all just suggestions though.

Ignore empty value textboxes  – See Screenshot named "EmptyValueTextBox":
When adding a variable filter, you can add more than one value to the filter using the "Add value" button. As a user, it was not clear to me that I then have to add a value in the appearing text box or remove the empty text box when creating a new filter. I would have assuming empty text boxes are simply disregarded when creating the filter. It would be good to think about whether it makes sense to automatically remove any empty value text boxes when the user clicks "Add Filter".

Validate input earlier - See Screenshot named "ValidateInputEarlier"

When I e.g. create a filter for a number variable, I am allowed to enter a String in the "enter value" textboxes. The "Add Filter" button is then disabled (even when other non-string values are added), but maybe we can not let the user add a string value in the first place? Especially when adding more than one value it's not obvious why the filter can't be created.

Add Information about type of variable to modal:

It would also be nice to add some sort of indication about the type of variable we're currently looking at. In our test cases, we always name the variables "intVar", "doubleVar", etc, but in practice it might not be obvious that I'm currently looking at a variable whose values are only String or Integer. Currently, the only indicators telling me that I'm currently looking at a number variable is the presence of the "is greater than" and "is lesser than" options. I cannot differentiate for example if a number  variable is Integer, Short, Double or Long.

Strip whitespace from number variable values:

When Filtering by a number variable the filter is not valid if I add e.g. " 1  " as a value, which disables the "Add Filter" button. It would be nice to strip the whitespace when adding a value to the filter because the user might accidentally add whitespace and won't understand why they can't create the filter.

Centering of Buttons in Correlating Variable Filter Modal – See Screenshot named "CorrelatingVariableFilter"

When adding a correlating variable filter, the searchbox is aligned with the variable value list whereas the "load more" button is centered on the modal itself, makes it all look a bit wonky.