Welcome to the “cross platform” world of Xojo.
Our app looks the way we wanted on Win and Mac… version 1.0 released after 3 years of development…
… where 50% of the time was wasted developing custom controls for almost every control as Xojo’s controls and many 3rd party libraries offered / available are either limited, out-dated, discontinued, stuffed with bugs, result in massive over-head…
The problem you mention above though, is easily solved.
Ps what are you using for the sidebar?