Attribute as list of list?

Is it possible to create an attribute as a nested list?

My attribute userCompanyInfo is a string concatenating other attributes in the following format:

def userCompanyInfo = "companyName=" + userCompany?.companyName + ":sirenCode=" + userCompany?.sirenCode + ":oriasCode=" + userCompany?.oriasCode

The result looks like this:

companyName=company1:sirenCode=siren1:technicalCode=techCode1

My customer is asking whether I can turn this string into a list as follows: [company1, siren1, techCode1]. However, as this attribute is multivalued, I want it to return SEVERAL lists.

So if user belongs to 2 orgs:

[[company1, siren1, techCode1], [company2, siren2, techCode2]]

Is it possible?