With Ctrl+B you can hide/show the entire button panel.
If you want to change how many button (rows and columns) the button panel should show need to edit the configuration for that manually.
Menu > Help > Go to > Config Folder
Select "MultiButtons.xml"
Select Menu > Tools > Text Conversion > To Windows Format (CRLF)
Then edit the MultiButtons.xml file.
the second line in that file contains the rows and cols. change them
<buttonpanel id="1" rows="4" cols="8">
You can change that to 1 or 2 rows if you want to have less buttons.