Just curious. Also, I'd like to know how high we've gone thus far.
I have had a similar experience, but the crash-on-load behaviour wasn't consistent and was cured by repeated attempts to open the app. I have since removed some folders that I figured I wouldn't be using often, and all's hunky-dory now. The total number of Rigs appeared to be unrelated to the problem; it was simply a matter of staying below the critical folder-count.
Interestingly, I was able to tell as soon as RM started loading whether I was above or below the count. If above it by a single folder (or perhaps only a couple - uncertain), the folder icons in RM didn't appear. If several folders or more above the limit, the disclosure triangles weren't there either.
Functionality was unaffected. Folders could be opened by clicking on the invisible triangles; they were still there.
Let's get to the bottom of this, eh? IMHO, we should start by examining whether or not there are folder and / or Rig-number limits, hence this thread.
Thank you, fellow beloved Kemperites!
PS: I really don't want to to and fro with support on this; it's not an issue for me but I can see a future where, as we all build our collections and refine them by sub-dividing them into more folders, we're gonna start running into this brick wall, if indeed it exists and is not unique to a small number of setups.
Rig Manager FW 1.5.16 'cause I'm still on Kemper FW 3.1.4