I am new to tryton and would like to know if it is possible to remove the create option in a many2one relationship.
The create option is activated only if the user has access rights to create the target model.
If you want to deactivate such button you will need to remove the create access.
It is possible to deactivate only one model?
Yes, the access rights are specified for each model. So you can activate or deactivate them.
Furthermore, you can relate access rights to a set of users, so depending on the grups of the user one may be able to create the records and others not.
Thanks for the explanation.
You can set on the field the XML attribute
Indeed the attribute is not yet allowed in the view until Issue 10840: Allow create/delete attribute - Tryton issue tracker
You may also consider using:
<field name="xx" widget="selection"/>
So the selection widget is used instead of the m2o, although the latter is better for searching.