So key will not be configurable then? Ahh well.
Possibly not on the very short term.
If / Whenever one contributes to the CEmu FLOSS code base some portable code to read and write key mappings from a file (presumably in a user's home directory, or e.g. AppData on Windows), leverage e.g. QKeySequenceEdit (suggested by Vogtinator), probably refuse multi-key sequences, and signal conflicts between mappings, certainly
FWIW, to me, Shift and Tab look equally unusual for 2nd. TIEmu uses Alt for 2nd and Control for DIAMOND, both of which were inherited from VTI.
I can't check VTI's mapping for the TI-Z80 series, as I can't seem to find out how to add new ROM images (TI-68k or otherwise) on a copy of VTI (both the original version and JM's much improved version) in a new place, after the initial stage where I added one old 89 TIB file and started it. The ROM wizard is not really what I want (and it supports only severely obsolete cables anyway); F12 provides me no way to add images through left clicking, right clicking or drag&dropping.