Right-click the Layout node in the tree and select Layout
View Filters.
The Layout View Filters dialog box
appears.
Click Clean up to delete all the unused filters.
All the filters that are going to be deleted are highlighted.
A message is displayed, prompting you to confirm if you want to delete
all the unused filters.
Click Yes to confirm.
In the Layout View Filters
dialog box, the unused filters are deleted. Only the filters
that are in use remain, as well as the Default filter, which is never
deleted.