I followed this tutorial but they didn't told me how to create own node.
Their code is creating item Edit/Insert Date but I want something like Edit/Insert/Date
From that tutorial it looks like I have to add but I don't know where because I tried to add it everywhere and it told me that I cannot extend that node.
Add your Insert menu inside an ItemSet.
<Extension path = "/MonoDevelop/Ide/Commands/Edit">
<ItemSet id = "Insert" _label = "Insert">
<Command id = "DateInserter.DateInserterCommands.InsertDate"
_label = "Insert Date"
_description = "Insert the current date" />
</ItemSet>
</Extension>