Dropper posts compatible with Shimano GRX ST-RX810-LA and internal cable routing

Hello! I own a gravel bike that I equipped with the Shimano GRX ST-RX810-LA lever. If you don't know, this lever was intended for actuating dropper posts only (and braking obviously)

I would now like to purchase a dropper post that is compatible with it, but I have run into the issue that most dropper posts require the cable head at the dropper post actuator, not at the lever.

Additionally, my bike has full internal cable routing (through the one piece handlebar and stem, headset, etc). I would therefore be locked into using an internal routed dropper post and the issue of cable tension arises. The shifter cable has to be long enough to hook into the dropper post's actuator out of the seat tube, but then also hold tension when inserting the dropper post into the seat tube several cms.

I am completely at a loss as to the function of this lever. I can't find any list of compatible dropper posts, and even the specifically marketed ones like the PRO Discover DSP 70 that claim they are GRX compatible do not show how to install them in the manuals. Its installation manual completely omits the GRX ST-RX810-LA lever and it very clearly shows the cable head end being inside the dropper post actuator.

Dear reddit, please help me. I really want to like this lever.