I just added a feature request as detailed below. I encourage you to do the same for whatever might meet your needs (and even if they are identical, it would probably help to have more requests):
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I would like to see different categories of markers that provide different behaviour within Sonar:
-> BEGINNING / END of song
So that when you playback or export an audio file, it will do so within these boundaries
-> SPLIT PROJECT markers
Adding one or more of these enables the option to split a single large project into many multiple projects. The name of each project could also be determined by the name given to these markers