If the coconut oil you found was hard at room temperature, you've got yourself a hydrogenated coconut oil, most likely with a melting point around 92F. Natural coconut oil will be almost entirely liquid at room temperature. Neither one of them, however, is going to be a good option for you if you're looking to slightly soften your chocolate, for, as someone already pointed out, they're incompatible oils. You may be able to get by adding 1-2% of a lauric oil to cocoa butter (chocolate), but it's a tricky proposition at best. There's an effect called 'eutetics' which is basically a hard way of saying that when you mix the oils together, you're going to get very unexpected and unpredictible results. Nonlauric oils such as cottonseed and soybean are going to be alittle more tolerated in chocolate, but i'd be hesitant to take it to more than 5% of the total fat. Keep in mind that the instant you've added coconut, soybean, or cotton seed oil to your chocolate, you can no longer call it chocolate (peksy standards of identity). Nutoils have a great softening affect on chocolates as well. You can add hazelnuts (or hznut paste) to chocolate and still maintain the SOI for chocolate.
If you're looking to just slightly soften your chocolate, anhydrous milk fat is probably your best bet. If you're not able to find that, you may be able to get by with just goood ol' store bought butter, but i've never tried that. If it's a milk chocoalte your working with, it's already got at least 3.39% butter in it already. you've got to be a little careful here, for as you add more butterfat to a chocolate, it becomes increasingly difficult to temper - however once you've achieved your temper, it makes it more resiliant to bloom. I'd be pretty hesitant to take the total milk fat contribution much over 6%. At 5-6%, youre going to have a noticeably softer chocolate.
Now, if you're looking to create a ganache type filling with longer shelf life (forgive me, I didn't have time to read the full thread, just scanned it), I've made fillings by using roughly 90% chocolate with 10% of a natural soybean or natural coconut oil. Here we're capitalizing on the eutetic effect to obtain a center material that never going to harden, even tho the vast majority of the fat is cocoabutter. It's shelf life will be near indefinate, as you've not got any water present (as with the cream).
White chocolate's going to have, at minimum, 3.5% milk fat, and in most cases it won't have much more than 4%. I'd think it'd take quite a bit of white chocolate to add sufficient milk fat to make a noticeably softer end product..
