(I've been trying off and on for decades to find the answer to this puzzle.)
This question provides some useful guidance for talking about asking someone on the phone to chill for a bit. But I'm interested in contexts where someone isn't merely waiting, but where the other party (or automated system) has in some sense suspended the call à la the good old-fashioned HOLD button. Things like
May I put you on hold while I fetch M. Dupont?
This customer-service line has had me on hold for 45 minutes.
Oh great, I put her on hold but now something seems to be wedged because it won't let me get back to her call.
Does "mettre en attente" unambiguously involve that suspension of a call and not a mere making someone wait, perhaps while one has merely put down one's phone.
And similarly, is "le bouton hold" unambiguously le composant d'une téléphone sur lequel on appuie pour activer la fonction dont je ne sais pas le nom ?