The click area for the Control + Click action on the glyph sections to bring up the Missing Glyphs dialog only works on the area to the left of the counter for filling out the glyph sheet. So on “Arrow 1/10”, I can’t click on the “1/10” area to bring up the missing glyphs dialog.
It took me a good while to realize what was going on, and this seems like unwanted behavior. I’ve recorded a video of the behavior in case the description above is hard to understand: https://imgur.com/a/mEwFYe5
Addendum to the above bug: this only seems to be the case for when using the internal touchpad on my MBP with CTRL + Click. Right-clicking with an external mouse doesn’t have this problem.