Hello fellow plumeria enthusiasts!
I am a novice regarding plumerias so please only judge me slightly for my lack of knowledge.
I have had the plumeria plant pictured with this post for about 10 days now. I had the plant shipped to me however it's beautiful root ball broke off in transit leaving not many roots behind. I neglected to add rooting powder to the roots before I put the plant in soil (I'm kicking myself). I watered the plant a moderate amount after potting and let it hang out in my window indoors for 7 days. I misted the stems and leaves intermittently over the 7 days also. After letting it situate itself for a week I moved it to my porch to get some full sun during the day while bringing it in at night. I used liquid Fertilome Root Stimulator on it today (diluted as directed on bottle). When I took a closer look at my plant and I noted the vertical wrinkles in the branches as pictured below. I would describe the consistency of the branches as springy; not soft but not firm.The leaves that were damaged during shipping have yet to perk up yet too. The new leaves growing at the tip of each branch have gotten bigger in size though since I've had the plant so there has been some evidence of growth.
I'm worried I misted the stems and leaves too much or I simply under watered it. Either way I feel terrible for the way it has started to between this plant and myself.
Any and all advice is greatly appreciated.
Thank you all in advance,
A very concerned plant mom 🌱

First things first. Your soil looks great. That being said, you have way too much of it. There aren't enough roots to absorb all the water in that large pot. I had a 3-4 year old established tree in the same pot. You're more likely to have root rot issues if you keep it in there at this point. I wouldn't go larger than a 2 gallon pot for what you have.
The plant seller usually removes all of the leaves before shipping. My advice would be to remove all of the larger leaves, so the cutting can focus on establishing a root system instead spending all of its energy on perking up all those leaves. The wrinkles will go away in time with the proper conditions and care.

1- repot in smaller pot. Clay pots are better choices IMO. They absorb excess water from the soil better than plastic.
2- remove the large leaves. Keep only the new leaf claws.
3- water thoroughly. Allow the soil to dry out before watering again.
4- give plenty of light and heat. A bright window may not suffice. It needs sun and warmth. At least 4-6 hours of morning sun is preferred while it is establishing. Then you can increase amount once it is established. You will know it has good roots when it starts growing more mature leaves.
Good luck!