the MBlock 5 GUI does differ from the Scratch 3.0 https://llk.github.io/scratch-gui/ mode.
The Block Palette Icons on Scratch 3.0 require less space. The continuous scrolling is a nice feature too. The placing…
Most important is that it will be much easier for the kids to switch from Scratch 3.0 to MBlock 5.0 when the UI design matches.
Please consider to change the UI to a better match or at least to add a toggle option to switch between the MBlock3 Compatibility mode and the new Scratch 3.0 look.