Nei,
Actually, no, there is no way. The task is the minimal "unit" of work so it will go either to CAPEX or to OPEX. Not both.
And normally companies do not want to leave that decision to end users (for compliance reasons) so Cost Type is not available "everywhere".
For Planning purposes, you start with % Capitalization at Team level, then you may go to capex/opex definition on Project/phase/activity/task level.
For Execution - unless I am very wrong - Clarity will assume the task's Cost Type for actuals. And you can only have ONE cost type per task.
If cost type is blank at Task Level, it defaults to the higher level, until project (For instance, Task->Activity->Phase->Project)
Hope this helps.
Alex