I have the same issue.  We only switched yesterday to QBO (will use the desktop app as my husband hates change) after 23 years of the desktop program.  We need units of measure on every invoice, we sell janitorial supplies by the case, or each, or box, or skid,

and it is needed for picking orders and packing slip sign offs.  I have a call scheduled for “On-boarding” with QBO staff tomorrow at 9 am and will see what they say. Fingers crossed it’s an option, we always had it on our desktop version.   Wish me luck!