Some processes like vmware make problems with smartrim,option to exclude some programs from smartrim is needed.
It is planned, as you can see in the change log, so far it is just a place-holder (http://en.wiktionary.org/wiki/placeholder) for it, you may choose to disable Smartrim until this function has been supported. :)
Quote7.9.3.1[beta] Enhancement GUI Added place-holder menu items and dialogs for user-specified SmartTrim thresholds and exclusions.
https://bitsum.com/changelog/pl/changes.htm (https://bitsum.com/changelog/pl/changes.htm)
Yes, it is coming soon. Version 8.0 will go out by the end of the month and this will be part of it.
I'll likely have this in a beta build in the coming days.