Several times now when designing forms, I have found myself wanting to fill additional unused space with larger inputs such as a multi-line text box, however as seen in the following example, this is not possible with the current row/column restrictions -
Ideally I would request a CSS-Grid like implementation, but I suspect this diverges too much from the power user-friendly approach of PowerApps. Instead, I would suggest something along the lines of 'column split' and 'row split' buttons, which I have illustrated below -
This would enable much more dynamic form control overall, and could be hidden under the ellipsis easily.
Regarding interaction with the split within the field property control, I would suggest two nested lists under the new control, on which fields could be dragged from the parent list.