Is it possible to create an event that would be in the transaction tab? Something like an "informational" event. I don't want it to get counted as an error, but I also don't need to time things with it.

Technically, "informational" events should normally come through Capture Message. You will see them in your issues tab with the tag level:info. However, those do count towards your reserved errors.

Here's an example of how they will show up in your Issues page:

If you want to do this through transactions instead, you can technically use custom instrumentation. You can then add any information you need as span attributes and/or tags. These will consume your reserved spans instead.