Hi Vladimir, I don't have any experience with plumerias. Hopefully someone will chime in to advise. I can only say when I grafted dormant apple twigs on a growing rootstock, they took easy both. Dormant cuttings to root, I have experience only with figs.

Plumeria does not need to go dormant but will do if it is cold enough. My hometown in India does not go below 50F and they flower and thrive all year round. They slow down a bit in winter and may be drop some leaves. So if your cuttings are dormant they can be forced out of it anytime with heat and light.

Looks like both cuttings have rooted! They both have a number of big, healthy leaves.

Great that it worked out and should help others with the same question.

I think the heat mat, and the warm of the room, are critical. My experience in bringing plumeria indoors for the winter, and kept next to a window in a cold room, is that they develop rot very easily. My solution has been to not water them at all, with an occasional misting of the leaves...that's the only way they'll survive in my house.

Heat mat + lights set on a timer for 12 hours or greater and barely moist soil. That should get them to root over winter.

Each cutting continues to grow. I now have them in a sunny window with temps 65 - 70 F and they seem happy.

Also started some from seed with heat mat at 75 F and supplemental light and they are growing very well.