Do I have to quit Storage Studio before installing an update?
Short answer: No. Open the newer version's disk image while Storage Studio is running and it updates itself in place and relaunches. It only accepts a genuinely newer, Apple-verified build, so an old copy can't downgrade it.
No. If Storage Studio is running when you open the installer disk image for a newer version, it recognises it, updates itself in place and relaunches on the new version — no quitting and no dragging to Applications.
It only does this for a version that is genuinely newer and verified by Apple as coming from us. An older or untrusted disk image is simply ignored, so opening a stale copy can never downgrade or replace your app.
The companion SS Bridge app updates itself the same way.