The lightsaber built by Kanan Jarrus had a blade length adjustment control. During the reign of the Galactic Empire, Jarrus kept this lightsaber hidden.
Rather than hang it on his belt by the belt ring, which would easily identify him as a Jedi, Jarrus stored it directly on his belt as two separate pieces, with the main body and grip of the hilt at the small of his back and the emitter shroud on his left side. Jarrus merely needed to insert the emitter section into the main body and twist to lock them together.
The lightsaber also had a low-power setting to avoid injuring sparring partners during practice. In this setting, the blade had a different shade of blue, and the weapon vibrated at a slightly higher pitch.