Sam Graves

That did it. Thank you.

Unfortunately, I am still seeing 0 results when using that search query.

I am going to Settings > Objects and Rules > then using the corresponding "Field ID" for this check box. Then I use the magnifying glass search field and use the example you provided above: 

custom_field_<5664670174221>:checked

It seems no tags were associated with the checkbox when it was set up. I thought the view would work by simply selecting TrainingMaterial > Is > Checked. I can set up the checkbox so that a tag is added but, are all of the tickets we've historically checked just lost and unretrievable? No matter how I search for these, the "Preview" search returns, "No tickets match your conditions".

We have this check box in our Zendesk sidebar but I don't know how to search for past tickets where this box was ticked. Does anyone know what the filter search criteria is for these checkboxes?

Screenshot here: https://i.imgur.com/PUGkLM8.png
(My image was a png and under 2MB but it still wouldn't allow me to upload it.)