Can I keep specific apps from being offloaded automatically

Unfortunately, it is not possible to select specific apps that should not be offloaded if "Offload Unused Apps" is activated. The only option is to disable the function and manually manage which apps should be deleted or offloaded.

You can deactivate the function here:

Settings → App Store → disable Offload Unused Apps.

You're welcome. Unfortunately, that feature cannot be fine-tuned that much, but it would definitely be smart if you could "whitelist" some of your apps.

You can always send a Feature Request feedback to Apple here:

Product Feedback - Apple