Hi there,
Thank you for the additional context.
If you wanted to disable GC after a level is requested to unload, you could disable the following CVar s.ForceGCAfterLevelStreamedOut as outlined in this documentation here. This will remove the forced garbage collection as a level is unloaded.
Otherwise, incremental garbage collection may be of interest to spread the work over multiple frames.
If neither of these options are appropriate for your use case, and you are looking to make an engine modification to manually disable GC on LoadMap, I can look to elevate this to a subjuct matter expert who can point you in the right direction.
Thanks,
Thomas