Hiya Galen, welcome to the BJS forum!
Umm… I have an idea. When you move camera.position.z, also move camera.target.z… the exact same amount. Might work.
You might want/need to set an invisible targetMesh as camera.target, and then just move targetMesh the same AMOUNT as you move camera.position.
Also, you might wish to set camera.lockedTarget = camera.target… or maybe camera.lockedTarget = targetMesh.position. THEN… MAYBE… you only need the slider to move the (invisible) target itself, and the camera will move WITH IT.
I’m not an expert in using camera.lockedTarget… sorry. You’ll need to read docs, search playgrounds, and do tests… to learn its full story.
Goof around with that stuff… and report back, as wanted. Other/Better replies might come soon.