None of the suggestions on how to get settings, and others for select all have worked for me. It does seem to matter which way you Open Outlook.
eg. using the outlook icon in Win10 Pro Edge new tab - hubs is automatically logged in first by password manager. His emails work fine with the side pane visible, and select all option available.

then when switching to my hotmail account I get the **** version that I can do nothing with except open & delete one message at time, and can't get a fixed display of the folders.
However if i copy the addy from password manager
https://outlook.live.com/
I get the select boxes/circles, but then have to fight to toggle the other folders/inbox display. One minute clicking on the bars under Home works to display them (if not selected properly the thing disappears again) yet another visit shortly after, as I test, one click toggles the same display to hold
