The six buttons on the right-hand column of the Second Tool Buttons (left/right arrows, smiley face, etc; cf. View->View Menu) can be freely redefined with Property Sheet->[Key].
For example, to define the lefthand arrow button the function to change into/from Landscape style, choose Option->Setup Parameters->[Key], and set Function: to Landscape, Key: to User2, then press [Define]. Continue with other definitions if necessary. Then press [Save] and lastly [OK]. The toolchips will be changed appropriately.
If these buttons are not displayed, toggle View->Change Tool Buttons.