The ability to use multiple actions in the action parameter by separating them with commas like we do in other parameters like user and include. This would be helpful when making hyper specific rollbacks or lookups while also wanting the effected actions to be rolled back in one go or for the results to be displayed in one look up.

Currently using action:container,block as a parameter in a lookup command gives an invalid action response.

I kind of see what you mean. I ran through the use cases I could think of for combining the actions, and most of them already have the combination of doing both the positive and negative action at once. And when it might be useful to do both kill and block at once, there's not much that would be affected by running one command and then the other.

The primary issue with this is that most actions are inherently incompatible with each other.

For blocks containing inventories, it may be better to either just add a separate action that rolls back both blocks + container inventories, or add another toggle to include this (e.g. #container)

But what's probably best is to just change a:block to include container contents by default. I'm not sure anyone really wants to rollback containers without contents (and if they don't want container logging, they probably already have it disabled in the config)