Hard, no : impossible.
I do hope that a future version of Dorico will make these handles smaller, in proportion to the size of the selected object, like Finale or Sibelius do perfectly.
It’s good to admit that Dorico may still have a few flaws, and as you’re all reasonable people, I know you won’t try to defend the indefensible. 
@ObiwanKenobi
it is best to formulate these wishes and suggestions as a Feature Request. You can tag them in this forum as those.
Until then I too would advise you to avoid the mouse for these fiddly adjustments.
The king’s approach would of course be the suggestions, @Christian_R gave further up in this thread. That way you would avoid manual corrections.
If they can’t be avoided, use tab to move the anchor point and the alt+arrow keys to do fine adjustments. Use the special key-combination for “Hide Invisibles” to avoid seeing the handles to check your adjusted appearance.
Good idea, but I don’t know how to proceed.
Could you explain to me ?
Or maybe hiding them while holding down a key?
Jesper
If you edit your post, in the upper right corner you can see the ‘optional tags’ text field. You can add feature request as a tag there.
Obiwan,
if you start a new thread, you can, before finally posting, add tags to the thread, like “feature-request” or “Dorico for iPad”.
“I would like the possibility to have smaller handles for fine adjusting grace note slurs.”
[edit] 
@Zalde was faster
Unfortunaltely, Jesper, while holding the key hiding the handles, the arrows to move the slurs no longer work.
Thank you very much my friend.
No, but you could get a peak of how it looks, release the key, and move a little more.
Jesper
Wonderful. Very handy ! 
I think it is time to close this thread, now. Thanks for all. 
They do, if you hold down the key a bit longer, and release the modifier key first. This will, at least on my Swedish keyboard where I have to press altgr and + at the same time. Pressing the key normally again shows the invisibles again.
Are we talking about the same thing, hiding the handles when you edit a slur in engrave mode?
Jesper
Yes it works. You need to define the shortcut for Hide Invisibles with a modifier and another key. And magically as @LAE explained, if you press the shortcut (modifier+key) and then leave just the modifier key and only after leave the other key, the Hide Invisible stays active. And the shortcuts for moving the control points remain active
Here a little demonstration (I have Shift+1 as my shortcut for Hide Invisibles):
Ha, what do you know? Stupid me for suggesting something that’s already there. Or perhaps, clever team for knowing what you want beforehand.
Jesper
I might be wrong, but I don’t think it is documented. I discovered it by chance!
Sorry. Ich habe nichts verstanden
In the manual, they say : " Tip : you can also hide/show individual non-printing elements permanently".
Great ! but how ? The manual is totally silent on this point. 
Il faut modifier le raccourci clavier de sorte que Hide Invisibles soit déclenché par une touche modificatrice (maj, ou alt, ou cmd) + une autre touche (par exemple @, celle qui est déjà affectée). Lorsque vous activez cette fonction, si vous gardez la touche modificatrice enfoncée après avoir lâché la touche @, le comportement Hide Invisibles va continuer, donc vous ne verrez pas les poignées, mais vous pourrez toujours les bouger avec les touches alt+flèche (ou autres). Un bug à notre avantage, en quelque sorte.
Merci Marc.
C’est vraiment tordu, hein ?
Ben c’est pas vraiment prévu, en fait… donc oui.
Et, cela marche.
J’ai attribué un raccourci à ces non-imprimables (Maj+@), et en laissant le doigt sur l’arobase, cela ne fait pas revenir ces maudits carrés.
Mais, il faut tout de même s’assurer au préalable qu’il n’y a aucun carré sélectionné, sinon, on joue les sculpteurs pour Beaubourg.
Bon. Il va falloir que la “Dorico team” améliore ça vite fait. J’expérimente Dorico depuis presque deux mois (mon essai se termine bientôt) et je crois n’avoir jamais autant fait de crises de nerfs… mon cardio va être mécontent. 
