It is possible to set the Minimum Launch Mass for the Interplanetary Launcher, and that is fantastic. The problem is that it always and only launches this exactly this mass, while the expected behavior is to launch once that mass is in storage, plus any additional mass up to 200kg.
So if the Launcher has 198kg of cargo, and the minimum mass is set to 195kg, what is expected is that it should launch its entire inventory. What happens instead though is that it launches exactly 195 kilograms, leaving a cumbersome and often unmanageable remainder ("crumbs") which interferes with future launches.
An alternative "solution" would be to rename the "Minimum Launch Mass" to "Mass Per Launch," removing the implication that mass above the specified limit will also be ejected.
Thanks for looking into it!
Load 200 kilograms or less cargo into an Interplanetary Launcher. Specify a Minimum Launch Mass less than the mass of the loaded cargo. Launch it. There will be a remainder.