JSFiddle - React, Tailwind, and code Playground

JavaScript

const obj = {
    Visualization: {
      Lower: [{ name: "Part", selectedValue: "60-000" }],
      Upper: [{ name: "Part", selectedValue: "60-000" }],
    },
    Holder: {
      Lower: [
        { name: "Part", selectedValue: "30-000" },
        { name: "Project Name", selectedValue: "45-000" },
      ],
      Upper: [
        { name: "Part", selectedValue: "22-000" },
        { name: "Project Name", selectedValue: "25-000" },
      ],
    },
  };
  
function deepSet(o, propertyName, propertyValue) {
    Object.keys(o).forEach(key => {
        if (key === propertyName) {
            o[key] = propertyValue;
            return;
        }

        if (Array.isArray(o[key])) {
            o[key].forEach(item => {
                deepSet(item, propertyName, propertyValue);
            });
            return;
        }

        if (typeof o[key] !== 'object') {
            return;
        }

        deepSet(o[key], propertyName, propertyValue);
    });
}

deepSet(obj, 'selectedValue', '0');

console.log(obj);