I “solve” this by putting braces in both lines and deleting the closing brace on the first line and the opening brace on the last line (there have to be some symbols inside the brackets otherwise you cannot erase just a single side of the bracket pair as far as I remember).

I would welcome a better and more correct way to achieve what you describe, but I am unaware of one.

Cheers,
Peter.

> On 13 Sep 2018, at 20:02, Jorge Fernández de Cossío Díaz <address@hidden> wrote:
>
> I have a long equation that spans multiple lines and has parentheses. Here is an example (I wrote this in lyx):
>
> <image.png>
>
> I know how to write equations in multiple lines in TeXmacs. But notice the outer braces in this example. They span multiple lines and have matching sizes. Is it possible to get this effect in TeXmacs? How?
>