I'm not familiar with the Kmise but many 5 string tenors have close string spacing - that may be playing against you here.
There are so many variables that go in to what people perceive as "too small" or "too difficult because it's so small" when it comes to fretboards and necks, it's hard to give a specific recommendation. But here are some things to think about, if you want to try to find an instrument that's easier to handle. I've spoken with many people who think they can't play a short scale instrument, only to discover after trying a few things that there are other factors that are the real reason why they didn't like a particular short scale instrument they tried.
1) String spacing at the nut (not the nut width itself, but the spacing of the strings) - wider usually feels easier if you have big hands or big fingers. Pretty straightforward.
2) Actual nut/neck width - for a given string spacing, some models have wider or narrower necks, although usually only a millimeter or two in difference. The extra space is basically on the outsides of the top and bottom string, the distance between the string and the edge of the fretboard. People who think they have trouble because of fat fingers sometimes feel more comfortable with more space here, since it gives the feel of a wider "platform" to fret against even if the strings themselves are the same distance apart.
3) Setup! Specifically, action at the 12th and at the nut. A uke with higher action will feel more difficult, regardless of the scale length. A short scale instrument with high action can be really hard to learn on. The same instrument with the action set as low as possible will feel easier. When many people play an instrument with high action, they tend to over-fret (push down harder than they need to) as a subconscious way to compensate for the strings being further away. If you're having trouble getting your fingers close enough together on a small fretboard, feeling like you have to push really hard to fret a note will make it much worse.
4) Fretboard radius - some people will find a radiused fretboard makes it easier to deal with a short scale length. Other people won't like them no matter what. Only way to know is to try it.
5) Neck profile. Some people with bigger hands will find a deeper/fuller neck profile fills their hand out more and gets their wrist and fingers in a better position to fret more naturally. A tenor with a thick D profile might be an epiphany moment if you're struggling with smaller scale instruments.
If your real motivation for trying a tenor uke is to have an instrument that's a little smaller overall and easier to travel with or keep with you, there are probably builders out there that would put a longer/wider neck on a smaller body, or some other variation, to get you something that works.