Thank you for posting!
To the best of our knowledge, the Lenovo Yoga 730 15" model cannot be charged via its Thunderbolt 3 port (it only supports data transfers and video output). Further to this, the system only supports a single display via the Thunderbolt 3 port. As a result, none of our Thunderbolt 3 or USB-C docking would be able to meet your needs.
The UD-3900 dock is not an option, as it cannot support two 2560x1440 displays.
An alternative would be our UD-6950H dock -> https://plugable.com/products/ud-6950h
The UD-6950H provides the ability to connect up to a maximum of two 4K displays (lower resolutions such as 2560x1440 and 1920x1080 also supported) to the unit’s built-in DisplayPort or HDMI video outputs (video cables not included).
The UD-6950H also provides six additional USB 3.0 ports, a wired gigabit Ethernet port and 3.5mm analog audio input and output jacks.
*** Important note - the UD-6950H does not charge the laptop. You will have to connect the original Lenovo power adapter to the laptop in order to charge the laptop while docked ***
Should you elect to move forward with a purchase and find that the dock does not meet your needs, we do offer a 30-day no-hassle return policy for all products sold by Plugable and fulfilled by Amazon.