Are wildcards available in setting up MiXplorer AutoTasks?
I am using version 6.54.0 of MIXplorer. Autotask does not have regex (widcards) options when deleting files. They are available for copying, moving and archiving files.
What you can do is:

Create a .sh file with for example the following command to remove files:

#!/bin/sh
rm -f internalstorage/backups/system/crap_*


Create a autotask, select Execute. Then on the File option, select the file created earlier.

The command above assumed that you know the path and part of filenames. Notice that I did not use the directory  /internalstorage/$/.crap.tmp as using * will lead to check all directories for .crap.tmp file.