'til now.
I generally don't open support calls with IBM unless the corporate usership reports it.
Just for the record, 32-bit on Windows 10.
I run into it in debug situations. So my current strategy is to use what I've got 'til it gets annoying; shut down Designer, restart Notes. Within Notes itself, if I haven't created a toolbar icon in Designer, Notes seems to figure it out.
I've also set aside the original bookmark.nsf so Notes created another. I'm hoping that doesn't become a requirement: toolbar customizations are destroyed when the bookmark.nsf corrupts, and I've never found a nice way to copy them into a brand new bookmark.nsf