You could add a Show All button ahead of the others and make that the default. When other filters are selected, it becomes deselected. W3Schools has a demo that might work well with a modification to allow more than one selection at a time.
There's a pattern for this type of UI: Filter chips
Material delineates the active filter state by adding a checkmark, and another click removes the checkmark:
you can also use an outline for more contrast:
Here's what I am thinking about:
Two buttons, one for adding a parameter, the other to do search, and a small button to delete parameter.
And I believe that Advanced Search is not bad. Just look at Github Advances search.
you could also do
[X] All Fruits
[ ] Zucchini
[o] All Veggies
If someone selects "All Veggies". disable the individual Veggies (ie gray).
If someone selects a single Vegetable, use a circle or disable the "All Veggies"
Use a clearer action than “Enter”. If the user is always going to add a parameter as Step 2, the button should say something like “Add”. When the system has enough input to perform the search, the user should then see a button that says “Search”.