Currently we can split a string into two parts (as mentioned in https://powerusers.microsoft.com/t5/PowerApps-Ideas/Substring-split-parse-a-string/idi-p/3682). However, there's no way to split a string into multiple parts. This limitation has been hit and reported in a few forum posts, and there's no workaround for that.
This function has been added to PowerApps since a few releases ago. For more information, take a look at the Split function.