The TX/RX filter allows you to exclude TX or RX streams from the log completely. Actually, individual layers are free; what you purchased was probably the "Layers" capability that allows you to attach any filter/conversion/analyzer layers to the log. The problem at hand can be solved with conversion layers, yes.

However! Before I show how to exclude everything except for the packets starting with 02??0A -- did you consider highlighting your prefix with the regex colorizer instead of excluding everything else? It's a much simpler approach, and it might be just enough to make finding your packets in the log easy. The result will look something like this:

For the screenshot above, I used \x02.\x0a as the regex.

If you insist on excluding all the packets that do not start with 02 ?? 0A -- this can be done with a conversion layer. Please provide some more information about the structure of packets in your protocol (the conversion layer would need to find the beginning and ending of each packets in the stream in order to decide whether to keep it or exclude it). Then I can help with writing a skeleton of the conversion layer that would do what you want.