Hi Romain,
Thanks for the message. There is no way to do that in the current version, but I've just added a way to do it and it will be included in the next release due out very soon. In addition to the built-in presets, you can now create custom presets by adding to the dictionary stored in iolite's 'Imaging/CustomGradientPresets' setting. The dict keys are preset names and the values are lists of QColors.
You could, for example, create a custom preset from Fabio Crameri's colour maps by using the following script to import the ".lut" file for the desired map.
from iolite.QtGui import QFileDialog, QInputDialog, QColor, QLineEdit
from iolite.QtCore import QSettings, QFileInfo
import pandas as pd
settings = QSettings()
gp = settings.value('Imaging/CustomGradientPresets')
if not gp:
gp = {}
fn = QFileDialog.getOpenFileName()
if not fn:
raise Exception('No file')
df = pd.read_csv(fn, names=['R', 'G', 'B'], delimiter=' ')
d = []
for i, r in df.iterrows():
d.append(QColor(r['R'], r['G'], r['B']))
name = QInputDialog.getText(None, 'Preset name', 'Preset name', QLineEdit.Normal, QFileInfo(fn).baseName())
if not name:
raise Exception('No name')
gp[name] = d
settings.setValue('Imaging/CustomGradientPresets', gp)
All the best,