I have financial accounting, there are fields, for example, "revenue in the client's currency" and "revenue in euros" and the compute field "revenue" in which these two fields are written through a slash, I want to make it so that, for example, when I group by month or by year, I have the same field displayed in the group header, only there was "revenue for the month or year in the client's currency / revenue for the month or year in euros", I understand how to calculate it, but I don't know how to display the char field in the group header

I found the basic_model.js file in which there is a constant AGGREGATABLE_TYPES and there is no char there, but are there any possible ways to change it?