I am using ExtJs 7.4(Modern toolkits) to create a grid with filterbar(with filter value) and groupfield(with group value), the filtered value not show on the filter bar. This is working perfectly in (Classic toolkit).
Here i attached my code in modern toolkit and classic toolkit.
modern toolkit: https://fiddle.sencha.com/#view/editor&fiddle/3g3u
classic toolkit: https://fiddle.sencha.com/#view/editor&fiddle/3g3v
I did manage to make your code work as the following fiddle:
https://fiddle.sencha.com/#view/editor&fiddle/3g53
You might need to refer on Ext JS Filterbar docs.
As you can see their default filter value were put on grid column config.