Is there a way to add and remove features from a grid?

In my example, I would like to have the default view be no grouping - but to then have buttons that can add and set groupField in the store. I have a working example with buttons, but when setting no groupField in the store, the group feature is still enabled but is empty - and just doesn't look right.

I'd also like to remove grouping as well.

Thanks for any help

Update: I have the below code that works, but of course this is hard coding items.items in the code, which I want to try avoid doing:

Code:
var disable_grouping = Ext.get('disable_grouping');
   disable_grouping.on('click', function() {
       grid.items.items[0].features[0].disable()
       assetStore.sort()
   })
   
   var group_by_location = Ext.get('group_by_location');
   group_by_location.on('click', function() {
        grid.items.items[0].features[0].enable()
        assetStore.groupField = 'location'
        assetStore.sort()
   });
   
   var group_by_owner = Ext.get('group_by_owner');
   group_by_owner.on('click', function() {
        grid.items.items[0].features[0].enable()
        assetStore.groupField = 'owner'
        assetStore.sort()
   });