I cannot reproduce the error. With my installation it works with or without accents. Could you check which OS and version you have (mine is below). As far as I know there is no special unicode setting in KNIME it should just work like it is.
You could check your local H2O context. After upgrading to 3.6 I had some problems and hat to restart KNIME once with an option “-clean” at the very top of the knime.ini
H2O Pojo to Mojo_v4.1.knwf (132.6 KB)
org.osgi.framework.os.name=MacOSX
org.osgi.framework.os.version=10.13.6
org.osgi.framework.processor=x86-64
KNIME H2O Machine Learning Integration 3.6.0.v201807060629 org.knime.features.ext.h2o.feature.group KNIME AG, Zurich, Switzerland
KNIME H2O Machine Learning Integration - MOJO Extension 3.6.0.v201805131030 org.knime.features.ext.h2o.mojo.feature.group KNIME AG, Zurich, Switzerland