Welcome to the forum.
What you’ve essentially described is Trading 212’s Pies feature. :freetrade: staff have previously mentioned working on something they’re at least for now calling Autopilot. It sounds pretty similar. The idea being that you automatically top up regularly and that amount is split into specified percentages of selected instruments. I don’t believe that the feature is a huge priority. Regular top ups are mentioned in the product roadmap. That would need to be an option before such a thing could exist.
If you search the forum for Autopilot - and ignore the stuff related to Tesla - you should find things related to it. Here’s one post from :freetrade: on the subject: AMA: Ask our CEO Adam your questions about our upcoming crowdfunding round 🗣 - #71 by adam