I want to save disk space without compromising the quality of recordings by using the opus codec. But Music Triggers does not play music in opus format.

Opus encoding is supported assuming you are using one of the supported file formats which can be seen on the wiki here. But if you are really looking to save space you can always stream via the redirect as mentioned here instead of or in addition to having local files

Opus can be played if it is in a mkv container. This works, thanks.