Group options of custom field in filter

-- HikaShop version -- : 3.2.1
-- Joomla version -- : 3.8.2
-- PHP version -- : 7.0.21
-- Browser(s) name and version -- : Firefox

Hi,
we have a custom field (Period) with lots of values representing different period of time and we would like to create a filter which groups them in a few options. For instance:

Early 17th, mid 17th, late 17th => 17th Century

So we end up with just 4 values in the filter which looks up in the for Custom Field Values.

Is this possible?

Thank you!!

Hi Philip,
thank you very much for your reply, but I'm afraid every time I try to save the values, they got cleared and not saved into the filter.

You may see the issue in the attached video.

Hi Nicolas,
thank you very much for your reply. I understand that. My question is if I can have these values grouped in a way so that in the filter in only shows 3 of them (one per century) but when performing the search, and you choose for instance 17th Century, it looks for items who has the value: Early 17th Century, Mid 17th Century ...

Is that possible out of the box?