Proper way to specify keyboard shortcuts/keybindings?

[scarlion1]

The default <Super>e works as expected, that is: press and hold <Super>, then tap e, (shortcut executed), then release <Super> whenever.

I was used to the right alt and period, though.  However:

• <Alt_R>. does nothing
• <Alt_R>period only works if Alt is tapped (pressed and released) followed by period tapped. However, in apps where the menu bar auto-hides, tapping Alt like this toggles visibility of the menu bar also.
• <Alt_R>+., <Alt_R>-., <Alt_R>+period, and <Alt_R>-period all do nothing.

Why does <Alt_R>period behave in this way?  and how to specify the shortcut so Alt can be held down while period is tapped?

Thanks

Edit: Actually <Alt_R>period seems to be ignoring the Alt and therefore simply tapping the period is enough to toggle emoji checker.  and i had to copy/paste one just to end that sentence!   back to the drawing board