When you have lots of calendars in Google Calendar, it can be overwhelming and difficult to see only your events. Paste this script into the Console of your browser to toggle only seeing certain calendars. I might make a browser extension to do this

specify_calendars_to_show_in_google_calendar.js

var calendars = Array.from(document.getElementsByClassName("NI2kfb qZvm2d-ibnC6b-bN97Pc DX3x9d"));

// ** RENAME THE CALENDARS IN THIS SECTION **
var calendarsToSee = ["NAME OF CALENDAR TO ALWAYS SEE 1", "NAME OF CALENDAR TO ALWAYS SEE 2"];
var calendarsToIgnore = ["Tasks", "Reminders"];

calendars.forEach(calendar => {

	if (calendarsToSee.includes(calendar.innerText) == false && calendarsToIgnore.includes(calendar.innerText) == false) {
		calendar.click();
	}

});