I use a piece of rope run through the middle of a pice of pool noodle. I can slide it up and down depending on depth.
I run the transducer cable loosley attached to it so it slides too.
I run the ropw through the transducer mount holes and anglw so it hangs level when suspended from rope.
Slide this down the hole and make sure the rope and not the ducer cable supports it.
i also use it in summer when jigging so I don't have to muck with the settings on the one mounted to my boat.
Similar to this one but I have a piece of rope to hold it and not the actual cable.:
