There’s a 20-pin generic TSSOP, and some specific ICs that happen to have a TSSOP-28 package, but no generic TSSOP-28 package. Example: https://www.infineon.com/dgdl/Infineon-6EDL04X0XXX-DataSheet-v02_07-EN.pdf?fileId=db3a304336797ff901367c18c18445af
Because of how parts are made generic footprints are somewhat unusual (each part has its own footprint file, although one in core parts can be used, that is unusual) so pick one of the ICs that has a matching TSSOP-28 and use that to make a custom part or create a new footprint.
Here, if you still need it with editable pins… (without gnd pad)
Generic TSSOP-28.fzpz (8.9 KB)
It shouldn’t be unusual though. Reusing the pcb file from core should be the preferred method for any part with standard footprint. And I mean referencing the core svg file in the part, NOT taking a copy, and adding the copy to the part.
Parts Editor has no way to actually directly do that though, as far as I know. It requires manual editing of the fzp file. It might be possible (not tried, guessing from symptoms seen) to trick Parts editor into doing it. If the copied pcb file that is imported into Parts editor is named to match the core part file, then that copy is deleted from the part (fzpz zip file), everything SHOULD line up.
That is, for a core svg footprint file like:
name the file to be imported into the part
Now, after importing into part editor, and saving/exporting the part, if the
svg.pcb.core_footprint.svg does not exist in the part, the core file should be used instead.
I completely agree. I think a complication is the swapping mechanism, if it can’t find the named file it will substitute something else that it thinks is equivalent (there is at one part in core parts whose pcb footprint doesn’t exist, but which has a correct footprint, a DIP I think, when loaded) so this may have unexpected results. I think the main problem is that this capability isn’t documented anywhere that I am aware of and parts editor doesn’t use it.