Checking the ideas platform, splitting bills is the most requested feature right now and even an pretty old one (from april 2018):
https://feedback.mews.com/forums/955622-billing-accounting/suggestions/36659347-split-charges-on-bill
There is no official mews roadmap – at least no public one but it seems that a lot of features in the area billing were published in the last weeks or are in the work right now . I would guess that there is a team assigned that has this specific part of the application as focus right now …
It would be nice if i could give my team some approximate information here, as this is one of the biggest problems and a frequent occuring one too . I am pretty sure im not alone with that .