Instead of a select dropdown, the variable filter modal should contain a typeahead element similar to Cockpit to select the variable name.

AT:

• Instead of a select element in the variable filter modal, there is an input field
• The typeahead shows a list of all available variables after clicking on the input
• The list shows 10 variables, to see the rest I need to scroll down
• After typing in the input field, the list is filtered to show only variables which name starts with the sting I typed in the input field
• I can select variable from the list with the mouse or navigate to the needed variable with arrow keys and press enter
• The selected variable's name is shown in the input field