Additional tempos text not displayed when Palette menu too shrinked

I use a vertical screen to be able to see an entire score page at once (very useful for orchestral writing).
So I need to use as few horizontal space as possible. Therefore, I hide the inspector and shows it on demand, but for the Palette, I only shrink it to display two columns of time signatures.
In these conditions, I see the Tempo menu with one column.

If I click on "More" (or Plus, I use french version), the popup menu contains a sort grid with one column and 13 lines, but the content is blank.

If I enlarge a bit the Palette, in the same conditions, I see all additional tempos texts.