The rail planner app is the last place where you should look for timetables, because it t's not reliable. Ferries are often not included. It's best to look at the operator's website. In addition, you don't need to add this ferry in the app, so the timetable is not really needed there.

Google search suggests that Grimaldi once operated a ferry between Savona and Barcelona, but the Grimaldi website currently doesn't mention it. You could ask them about it.

Another option is a ferry from Genova to Barcelona, operated by GNV. Or from Civitavecchia to Barcelona, operated by Grimaldi.

Grimaldi have an Interrail discount, see:

https://benefitsportal.eurail.com/benefits/grimaldi-lines/

But also check for fares without Interrail discount; a normal saver fare could be cheaper if available.