Hi,

To hide and unhide the trash icon on a one2many field in Odoo 10 based on a condition, you can use the attrs attribute to make the icon invisible based on the specified condition:

attrs="{'invisible': [(condition)]}".

For example:
<button name="unlink" type="object" icon="fa-trash" string="Delete" attrs="{'invisible': [('your_boolean_field', '=', False)]}" />

Hope it helps