How to add a filter today in sales order search mode
The domain should be a list of tuples. You created a list, but forgot about the tuple. In addition, you made a typo ("doamin"). The code below should execute without errors:
<filter string="Today" domain="[('date_order','=',datetime.now())]"/> I do not think, however, that is what you want. date_order is a datetime field. This will select only orders with the current date and time (therefore not all of today's orders).
Here is an example of the correct Today filter in the datetime field (based on the stock.move.search in the stock module):
<filter string="Today" domain="[('date_order','>=', datetime.datetime.combine(context_today(), datetime.time(0,0,0))), ('date_order','<=', datetime.datetime.combine(context_today(), datetime.time(23,59,59)))]"/> Basically, date_order should be greater than or equal to the beginning of the current day (00:00:00), but less than or equal to the end of the current day (23:59:59).