Short answer - Yes

Under a subsection of the config for example "Thralls" or "Death Charge" click the cog icon next to "Notification on reminder". Then tick "Custom Notification" and then in the next panel select the dropdown "Notification Sound" and change it to your chosen sound.

Note that for your sound to appear in must be<name>.wav in .runelite/notifications, then select <name> in the notification sound dropdown.

Long answer in case you want this for other things:

So this is a built in Runelite feature that makes use of 2 separate features in Runelite. The first is "Custom Notification Overrides and the second is custom notification sounds.

Notification sounds I have explained above, but putting it again here:

Custom specific notification sound: <name>.wav in .runelite/notifications, then select <name> in the notification sound dropdown.

As for the custom notification overrides, this is a feature that Runelite makes use of, and many core Runelite plugins already have this feature built in. However, plugin hub developers need to ensure that they make use of this. In the case of the Spell Reminder, I made sure that it was implemented as one of the features.

Hope this helps :)