So it has been well over a year (August 2020) since I fired up Kerbal Space Program. After having 745+ hours invested it was time for a break. At lunch today I decided to jump back in and upgraded KSP to 1.12 and then had CKAN.EXE update my modules (KIS at 1.28 and KAS at 1.10). Things seem to be working as before except for trying to connect a winch connector to a connector mounted to another vehicle. I can use an Engineer on an EVA to grab the connector at the winch and then extend the cable and its connector out to a connector on another vehicle. However, the only option is Y to drop the connector. I no longer see a menu option to connect the winch cable connector to the connector mounted on the second vehicle (basically allowing the tethering of the two vehicles together). Actually, it appears I cannot even select the connector mounted to the fuel tank, hence no context menu to pick the connect option from.

Luckily I had another connector that I was able to select and connect to on an adjacent module. However, once connected it doesn't appear that the two vehicles are acting as though they are docked, like they used to. I can select the fuel tanks and pin them for both the refueler (with a winch attached) and the fuel tank on the base station (with the wince cable attached), but I am no longer able to move fuel in/out using the winch as a "hose". The in/out buttons don't appear as the system is acting as the vehicle isn't docked.

I used this feature to simulate fuel rovers going between Mun bases and refueling ships that would take ore and/or fuel back up to orbiting space stations. I was treating the winch like a hose reel. Once I connected the winch cable connector to the connect on either the fuel tank on the base station or the refueling transport I could transfer fuel. Unfortunately, none of my refuelers on Mun, Minmus, and Duna work anymore. Since it has been over a year I have no idea in which version the behavior broke...

One year of not being in the game is a good reason to refresh the knowledge on the game and the mods. Have you visited the forum thread? There are videos that demonstrate the parts usage. Also, I'd recommend reading Wiki. If you won't find answers to your questions on these resources, please let me know - I'll do my best to update the docs.

Admittedly when reviewing the forum thread and the wiki I missed in what version connecting via winch to a connector now fails to dock the two vehicles together. I'll try to review at which point / release version that occurred.

Ability to dock via winch was purposely removed. Winch docks to the attached vessel only when the cable is fully retracted. RTS and TJ parts can dock via UI.