How to store fresh coriander for future use, outside refrigerator, so that they don't lose their taste?
Buying coriander whole rather than ground is probably your best bet. As is the case with allspice and coffee, they're bound to eventually lose flavor, likely to light/heat/moisture, fresh grinding will bring back some of the spark.

If you're using fresh from the garden coriander you're not out of options. There's the floral option, and also the same rules apply here for drying herbs if you're willing to go down that route. If the fridge/freezer simply isn't an option, and having a bouquet of coriander isn't in the cards, then I would just hang them upside down in your basement/closet and then keep them in airtight containers away from direct light and heat.