Hi @zabramovich ,
Here’s a link to the [https://download.lenovo.com/consumer/mobiles_pub/yoga720-13ikb_yoga720-15ikb_hmm_201702.pdf|service manual] for the laptop.
Scroll to p.61 to view the necessary pre-requisite steps and then the procedure to remove the LCD panel.
I’m not sure if installing a 4K panel would even work.
I cannot find any information as to whether or not the GPUs (Intel and nVidia) as installed in the laptop support 4K resolution or even if there are compatible drivers available. Plus the fact of whether or not the LVDS cable will a) plug into the motherboard connector at all and b) if it did whether the cable connection wire functions would be the same for both display panels.