Multiselect fields output choices in a semi-colon delimited sting:
Flows often need these strings to be converted into a collection of strings that can be looped over or passed to an action.
The new ConvertToStringCollection builds on the previous ConvertCSVToStringCollection. It lets you pass in a delimiter (a fancy word for “the character that’s used as a separator). So you can pass in ; to get a collection of strings from a multiselect picklist. You can also pass in other popular delimiters like comma and even space.
This action is available in the new version 1.1 of the String Converter package.