After you used the new f3+f4 thingy to change gamemode, you will have to press 2 time the f3 button to open or close the f3 menu
steps to reproduce:
change gamemode using f3+f4
press f3 to open or close f3 menu
nothing happens
press f3 again,
the f3 menu opens
Thank you for your report!
We're actually already tracking this issue in MC-183776, so I resolved and linked this ticket as a duplicate.
If you would like to add a vote and any extra information to the main ticket it would be appreciated.
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