My understanding is that the charging profile is different for each of these types of battery’s.
You may be able to set at the lowest charge rate but even if that is possible you are unlikely to get the best out of the setup.
It could result in either one being over or under charged.
Others on the forum will know more about lithium charging than I.
Not really the Lithium will never get fully charged on a Gel setting and the Gel setting on the charger will have an 8 to 16 absorption phase which is not that good for Lithium. The Lithium charge voltage is too high for Gels and has either a short or no absorption phase.
And with them connected in parallel, the Lithium will be feeding the Gel due to voltage differentials.
No, as Lenny HB says. However if you have a lithium and a gel battery, you could have some arrangement where only one of them is connected at any one time, using a battery changeover switch. Then you'd have to work out how to charge them. Either switching the chargers and resetting the profiles, or having two separate chargers. It would all be a bit complicated, but not impossible.