In response to the questioner's concern, I just created a tag for [trs-80]. (See Did Radio Shack initially attempt to get a monopoly on commercial software for the TRS-80 Model I?) He specifically mentioned in a comment that he had lacked the privilege to create a [trs-80-model-i] tag. The tag he was suggesting paralleled a pre-existing tag, [trs-80-model-iii]. However, I saw that the Model III tag has only ever been used once. I also noted that the TRS-80 Color Computer already has a separate tag, [color-computer], which is used for many questions.
For my new tag's description, I wrote that it was to be inclusive of the z80-based TRS-80 computers, the Model I, II, III, and 4. The other TRS-80 computers (Color Computer, Pocket Computer, Model 100, Model 2000) all have very separate designs and IMO should use some other tag.
I suggest that the pre-existing [trs-80-model-iii] tag be either retired or made into a synonym, and its question be edited to include the new tag.
After a little more research, I see that the Model II, while a z80-machine, was an outlier in the Model I, III, and 4 family. It was designed for the business market and had a built-in 8" floppy drive. It had its own business-centric descendents, including the Model 12, Model 16, Model 16B, and Tandy 6000. From Model 16-up, the machines added a 68000 cpu and could switch to run Unix. So I probably should remove the Model II from the description for [trs-80], but will wait for feedback.