Pick a sound pack, set how loud it is, and mute what you don’t need. These sounds are app-wide (call chimes and message pings), and volumes stay on this computer.
At the top right, Save as pack… asks for a Name and saves your current sounds and settings as a new pack (Save / Cancel).
Two groups, each with a group switch (“Call sounds” / “Message sounds”; turn off to mute the whole group). Expand Customize 10 sounds (Call) or Customize 2 sounds (Message) to set each sound’s source (a built-in tone, “From sound pack”, or Upload file (audio, ≤256 KB, ≤5 s)…), its volume, a Test button and its on/off switch.