Best answer by jat0rz
If you are trying to reset Streamlabs OBS, you can do so by going to Settings --> General and Delete Cache and Restart.
If you are trying to get rid of your scene collections, then before you do that, do this:
1) Click the dropdown arrow next to you scene collection name in the bottom left corner.
2) Click MANAGE ALL.
3) Create a NEW scene Collection.
4) Go back to MANAGE ALL.
5) Delete your other Scene Collections by putting your mouse pointer over them and selecting Delete.