https://www.curseforge.com/wow/addons/worldbosstimers?comment=294

From report:

It doesnt expand enough for some of my characters it seems. it just 2 small 2 see the timers of the trackers when there is like 5-6 bosses on the list. maybe its something with the UI config on the chars and Elvui dunno

So probably ElvUI related (i.e. low prio), but I haven't looked into it yet.

Tested with elvui-12.98. No issues. The window expands as expected (and size it's not clear from the problem description, font-size is also unchanged).

Closing since can't replicate.