The lack of resolution for user curves limited my use.   There were only 8 different inflection points in a user curve and ideally I wanted to be able to map all 128 (0-127) inputs to all 128 (0-128) outputs.   

What I ended up doing is learning more about usage of the preset curves and mostly got them to do what I needed and/or changed around what I was trying to do in order to "fit the (available preset) curve".

There's still 32 user curves in M.

https://manual.yamaha.com/mi/synth/montage_m/en/om02screenparameters0050.html

But now there's more resolution to the inputs and outputs.  0-1023.  However, the same 8 inflection points so even more constrained given we have even more points but the same low number of ways to cut them.

I think the perceived limit from Yamaha's perspective is how to quickly program -- on the keyboard -- these user curves.  I could see how having 1024 values to set could get unwieldy.   There's always a solution and maybe 32 would be enough (baking through 4 pages to complete the full curve -- including an option to have 8, 16, 24, or 32 inflection points.  Where you could still have one page to edit all (like today =8) or two pages (...=16) or three pages ... you get the idea.  And then allow offline editing (some mapping of SYSEX registers) to allow for software by 3rd parties to come up with an elegant way to give full resolution.

So to summarize - since I couldn't get what I really wanted out of user curves -- I didn't use many of them.  Mostly I found the "resolution" (granularity) of the user curves to be too coarse.  If I was able to more fully program user curves then 32 may get limiting.

I wouldn't mind having 32 total global user curves if each Performance could have its own set of user curves apart from the "global" 32.   Total this would allow for 64 curves for each Performance.  32 of them defined in the Performance itself and 32 at the system level.   Register space at the Performance level would get high if the resolution (# of inflection points) was much more than 8.  Still would like to see more granularity.

I wouldn't mind having 32 total global user curves if each Performance could have its own set of user curves apart from the "global" 32.   Total this would allow for 64 curves for each Performance. 

that would have been alright.

Using in combination mod control curves for part and m c curves for elements can saves some user curves.

I mean combination mod control curves for part and m c curves for elements targeting the same parameter.