Unfortunately this friend is extremely autistic and is having a full-blown panic meltdown due to "they can't see all their tabs without clicking a button". I've been encouraging them for several years to slowly migrate to firefox as they've been suffering crippling performance issues and memory leaks with chrome, but instead of heeding my advice (to slowly acclimate themselves to differences like this) they just found a tutorial to import everything at once and now they're overwhelmed with all the differences happening at once and panicking.
I found the browser.tabs.tabMinWidth setting in about:config and suggested they set that to 0 but it's only a compromise at best and I doubt they will end up sticking with firefox at this rate to be honest.