Proposal documents in two languages but system GUI in several languages

Summary:

Content (please ensure you mask any confidential information):

Hello,

I followed this link: https://help.bigmachines.com/BMIHelp/#DocumentDesigner/Document_Designer_Languages.htm?TocPath=Document%2520Designer%257C_____9

in order to have a document proposal in multiple languages.

I created an attribute proposal language of type Language but the entries are not editable and corresponds to all the supported languages in CPQ, resulting in the quotation page like that:

However, we want the supported languages in the system to not be changed, but we want also to choose which languages to display here since we have the document only in two languages (French and English) and these are the languages we want to be shown.