Currently it can not be done from the wui so someone would have to write the code to make that happen.
The core team of developers in the IPFire project is small and they spend their time doing work on the next generation IPFire3.x and fixing bugs and overcoming new security issues identified on the internet for IPFire2.x
Other contributors to IPFire who have the capabilities and are willing to do the coding work are always welcome and the wiki provides information on joining the development mailing list, the git source repository and how to submit patches etc.
If you just want to run some scripts on a periodic basis there are directories where you just place that script and it will be run with a specific frequency automatically. Nothing further needs to be done other than placing the script you want run in the appropriate directory.
The directories are under /etc/ and are named
fcron.minutely
fcron.weekly
fcron.daily
fcron.weekly
fcron.monthly