Do you mean that you have some tournaments where the blinds don't increase regardless of how long you play?
Those won't be separated automatically, but you could add a new tournament description for them if you like.
You would need to add the description and change the type of these tournaments manually.
Go to View Stats > Tournaments > Results and click the Edit Tournament Results button in the sidebar.
In the window that opens select one of these tournaments.
Click the spanner/wrench icon to the right of the "Desc:" selector and choose Add Description.
In the text field at the bottom you can add whatever text you like to the description, so you could add a code to the end of the name to use for these tournaments. (e.g. add "ULB" to the end for Unchangeable Levels Blinds, or whatever you want)
Click 'Add' to save your new description.
You can now select the tournaments of this type with shift-click or control-click and change the description.
EDIT: I just remembered that unfortunately the filter for specific tournament types isn't in place yet.
I have reminded the development team about this, but in the meantime adding your own text like that won't allow you to filter for these tournaments.
What would work is to use one of the built-in flags for a type of tournament which you never play. For example, if you never played at Full Tilt you could tick the "MATRIX" option instead of typing. Alternatively if you never play push-or-fold tournaments you could tick "POF".
This will allow you to filter for that flag.