The axes in 2D and 3D spectra can easily be flipped by typing XY, XZ or YZ to flip the axes in question. You can also go to the View menu and select Current / Copy with X-Y Axes flipped (and the equivalents for the other axes). Because each spectrum display module has a fixed arrangement of axes, the spectrum is not flipped within a module, instead a new module with flipped axes is opened. The original module can then be retained or closed, as desired.
An alternative, which also works well for 4D and higher dimensionality spectra, is to type FA (for 'flip axes') or go to the View menu and select Current / Copy with Axes flipped .... This will bring up a small dialog box in which you can select the axis ordering to which you would to move.
The default axis arrangement is to keep the directly detected dimension on the X-axis, place any dimension with the same isotope code on the Y-axis and the remaining dimension along the Z-axis. Triple resonance spectra are displayed in an HxCyNz arrangement. You can change the default axis arrangment for a spectrum by double-clicking on the spectrum in the sidebar to bring up the Spectrum Properties dialog. Move to the Dimensions tab and select your preferred default axis ordering for this spectrum under Axis Ordering.
Alternatively, you can go to the global preferences in Project / Preferences (or type Ctrl/Cmd ,). In the Spectrum tab you can change the Axis Ordering from Use Spectrum Settings to Always Ask. In this case, whenever you open a spectrum in a new spectrum display module, you will be asked what axis arrangement you would like to use.