Some comments and ideas:
1. # Base change:
Currently to change base, you press [f][#][H] or [f][#][D] or [f][#] or the obvious for any number base in range.
Why is B not defined to be a shortcut for binary?
Either way, upon pressing [#], on the emulator, appears a menu with ->, VARS, ST ... and it goes into entry mode with no indication that you are expected to press to change base. I know you always say that one should know what you want to do, but the rest of your calculator is ergonomically optimised, why not make this clear too?
If there would have been no indication (at all), one needs to remember, but with irrelevant text and keys marked, it is misleading. The IJKL registers, ST.X..through ST.D, and the VARS item and the [->] do not work if you press it and do not belong there.
On the real hardware, it may be less of an issue, but still an issue, as the misleading data is less, and only the unresponsive menu line with --> VARS ST.X ST.Y ST.Z ST.T would appear, which is misleading.
I would have liked to see an indication on a menu for HEX, DEC, BIN, OCT and # instead of this. I realise this possibly will mean a menu rather than going straight to the TAM input screen. Maybe a menu with:
HEX, DEC, OCT, BIN, NN
where NN in turn calls the existing function which brings up the TAM screen or a modified one for custom bases.
Possibly on the [f] shift of the menu, the common WSIZEs as in
4 b, 8 b, 16 b, 32 b, 64 b, NN
where NN again calls the existing WSIZE input TAM screen or a modified one for custom sizes.
2. R <> P
[RESET]   [>P] does not show the text on the left "r" & "angle" any more. p. 120 of the OM shows the texts.
[>R] does correctly show "x =" and "y =" on the left hand.
3. OM p. 114
" ... converts rectangular coordinates to polar ones (cf. pp. 19f)". The link is incorrect.
I noticed the pattern in your menu names X.FN, P.FN, a.FN. An idea may be to consider the name "RBR" in the same way to "R.BR" or something like that, if maintaining the pattern is important to you.
The global bit status view command STATUS (in the FLAGS menu) for the 112 flag bits has a very similar role than RBR for the 112 registers. Both are very useful and powerful tools indeed, to such an extent that you may want to bring the bit viewer to a key, with similar type of naming.
Elec Eng, South Africa
C43 (WP34C) on DM42 sn. 03818 & 06199 for complex math, HP42S; HP32Sii, WP34S&C, HP28C, HP35s, EL-506P, EL-W506, PB700; owned FX702P & 11C; used HP67 & HP85; iOS: 42s Byron, Free42, WP31S/34S, HCalc.