I also keep my "stuff needed for engineer upgrades" outside of TCE. It's too complex to keep in there with my desire to keep track of if it is a data or a mat, where or how it's found, what upgrade it's for, and how many I have/need. Excel works fine for that.
After thinking about this further, I'd tend to agree, we could do with a TCE like tool for Engineers, but I'll use the spreadsheet for now, it does a good job.