Is it possible to filter on hidden columns using the filter plugin methods?
Yes, it’s possible.
In a demo, we hid the second column and add filter “Greater than” 95 on it - https://jsfiddle.net/5bcy6pro/10/
If you click button
Show column you can see that the second column is filtering.
And here is a link to Filter itself in our docs - https://handsontable.com/docs/7.4.2/Filters.html