In new (4.9+) panels there are two vertical modes, one with horizontal and one with vertical plugins. Orage plugin should rotate its labels 270 in the vertical panel mode to match the look of other plugins.
Created attachment 4106 A patch implementing this feature. It should work with xfce panels 4.8+ (version checking was added in 4.8).
Created attachment 4107 The same patch + centering labels in wide panels. This patch consists of two commits: 1. A commit that implements the feature described in this bug report. 2. An unrelated (sorry) fix of over-spread labels in wide panels. When I place a two-line orage plugin in a wide horizontal panel, the labels expand to fill the whole width of the panel. This is rather ugly and not very readable. The fix (2) places all labels in another vbox which puts them near the center line of the panel and preserves their normal spacing.
Ok, thanks for the fix, but this needs to wait until I create 4.9 or 4.10 version of Orage, which may take while. Current 4.8 is still compatible with 4.6 Xfce, which does not have the version check macro.
Created attachment 4112 Label rotation and centering, should work with v.4.6 I've modified the conditional. It should now work with versions < 4.8.0 too.
Ok, this is now available in git version 4.11.1. It works manually though, so it is not automatic.