Yes, these are just the "missing structure" pseudobonds and there are many different ways to hide them. 

<https://rbvi.ucsf.edu/chimerax/docs/user/pseudobonds.html>

One way is to use Model panel:  use the disclosure triangles to reveal the model hierarchy including the "missing structure" pseudobonds and then un-check the display checkbox for that model, see screenshot attached.  Another way is to use the "hide" command to hide that model, e.g.

<https://rbvi.ucsf.edu/chimerax/docs/user/commands/show.html>

hide #1.1 models

or

hide #1.1

(if you use the second command above, the display checkbox is still checked, since the checkbox hides at the model level whereas that command hides all the individual pseudobonds while technically leaving their model displayed)

Or, if there are more than one and you just want to hide a specific one, then you can select the one you want to hide with Ctrl-click and then use command

hide sel

There was a bug that made pseudobonds between ribbons hard to select, but if you get a recent daily build that problem has been fixed.

I hope this helps,

Elaine

On Apr 28, 2021, at 6:51 AM, Gabriele Cerutti <gc2695@columbia.edu> wrote:

Hello,
I am displaying a protein molecule in cartoon representation and chimeraX automatically shows dashed lines for chain breaks (see attached).
Is there a way to hide these dashed lines?
Best,
Gabriele