choose few options for each filter

-- HikaShop version -- : 2.6.2
-- Joomla version -- : 3.5.1

I wish to improve functionality by adding possibility to choose few options for each filter instead of one, even if one option is already chosen.
What do I have now:
filter "Производители" (Manufacturers) has 5 options (Feather, Parker, Merkur etc). Once I choose 1 options, other options disappear. Photo 1 and 2 show the problem. leza-shaving.com/ru/safety-razors
What do I want:
Once customer chose one option (for example Merkur), he still can choose other options of chosen filter without excluding Merkur (additionally choose Parker and Feather options).
Example: hotline.ua/auto/avtomobilnye-akkumulyatory/16531-5166/

I know that I can partially implement it with "Filter" button, like it`s done here leza-shaving.com/en/straight-razors . thought a customer can`t add options, once he chose some. He is forced to remove filter and set it up again with a new list of options.
It`s obsolete functionality and I wish to remove "Filter" button functionality entirely.

Thx for your help in advance guys

Hi,

There is no option to have it like you want without the filter button. It would require some modifications to be done in the file administrator/components/com_hikashop/classes/filter.php in the display function of the hikashopRadioClass class.