T1 and T2 are known as ‘Tools Layers’, and were introduced with the release of version 0.9.17.
Tool Layers
These are layer colors that will never be sent to your laser, and are designed to be used as rulers, guides, alignment tools, paths for text, image masking, and so on. They will never be sent to the laser, have no cut settings, and you can decide whether or not they are using when calculating job origin. For example, if you often draw a frame around your design so you can center it properly, but set that layer not to output, you’d now make a tool layer set with ‘Frame’ enabled.
No, there is not currently. What are you designing? 28 Layers as well as ‘Power Scale’ for individual shapes provides a significant number of options for control. Help us to understand this project, we may have suggestions that will not require additional layering of this job.