Refresh rate and time in second can be hard to get along in the UI.

    const changerr = (e) => {
      const rrs = this.prefs.refresh_rate_sec === 1 ? 5 : 1;
      this.prefs.refresh_rate_sec = rrs;
      e.target.textContent = `${rrs}s`;
    };

    const button = document.createElement('BUTTON');
    button.addEventListener('click', changerr.bind(this));
    button.textContent = `${this.prefs.refresh_rate_sec}s`;

    div.append(button);

I know my UI isn't good either but it's something I settled with using in my custom client, there's "Refresh interval" with choice between 1s and 5s (literally a button toggling between them).

I'm not sure what UI can be so I'm just brainstorming.

im just following what's already available in the preferences. since the preferences expects a number (not a boolean) i determined it is more appropriate to use number input with min max and steps rather than a toggle button (or even a select box). im currently using 2 seconds now and a toggle between just one and five is already unusable for me.

I agree with @ivanjx that a select box (1/2/5/10/20/50?) is more appropriate.